Nobody can say for sure what causes a person to kill.  It could be a hereditary mental
instability, ideals learned at a young age, or just situational experiences.  Some of the most
deadly killers in history were mob enforcers and some military men, but most were
psychopathic serial or spree murderers.  The most heinous crime an individual can commit
is taking the life of another. 

Most murders are based around revenge, money, and deception, but a serial killer is a
different type of beast.  There are countless horrible killing sprees in modern history, which
made it difficult to select only ten cases.  Here is a list of the events surrounding ten of the
most deadly killers in world history.

Muhammad was born in New Orleans, Louisiana and enlisted in the National
Guard at a young age.  He then became part of the U.S. Army and was
explicitly trained as a mechanic, truck driver, and specialist metalworker.  He
was also a qualified expert with the M16, which is the Army's standard
infantry rifle.  He was ranked in the highest three levels of marksmanship.
Muhammad was discharged from the military in 1994 and turned to a life of
crime, often engaging in credit card and immigration document fraud
activities.

For a three week period in October of 2002 Muhammad terrorized people in
the Washington D.C. area with his Bushmaster XM-15 semiautomatic .223
caliber rifle, equipped with a red-dot sight.  The weapon had ranges of
between 50 and over 100 yards.  Using a small hole strategically placed in
the trunk of his car Muhammad and his accomplice Lee Boyd Malvo shot
and killed eleven people and critically injured three others.  It was a
terrorizing time for people living in this area of the United States, as men,
woman, and children were being murdered at random.  After three weeks,
investigators closed in on the two suspects and arrested them at a rest stop
with the murder weapon in the trunk. 

Calley was born in Miami, Florida and had a normal childhood.  After
completing large amounts of training he was named Second Lieutenant of
Infantry for the United States military in 1967.  He was not highly regarded
as a platoon leader and was disliked by many soldiers.  On March 16, 1968
the My Lai Massacre occurred in South Vietnam.  U.S. Army forces
conducted a mass murder of over 500 unarmed citizens.  The majority of
which were woman, children, and elderly people.

Many of the victims were sexually abused, beaten, tortured, and some of the
bodies were found mutilated.  William Calley was charged with ordering 26
men to kill everyone in the village.  He was also involved in carrying out the
murder and faced serious war crime charges.  In 1971, Calley was convicted
of premeditated murder of Vietnamese citizens and sentenced to life in
prison.  He was pardoned by President Nixon on two separate occasions
and was only incarcerated for three years. 

Hamilton was born in Glasgow, Scotland in 1952.  He was adopted at an
early age and seemed to be a quiet, but normal child.  However something
was terribly wrong with this man and on March 13, 1996 he entered the
Dunblane Primary School and killed sixteen students and one teacher.  He
also injured fifteen people.  He used two 9 mm Browning HP pistols and two
Smith & Wesson .357 Magnum revolvers.  He had an altering combination
of full metal jacket and hollow point ammunition.

Upon gaining entry to the school Hamilton immediately made his way to the
gym and opened fire on a class of five and six-year-olds.  The majority of
the victims in this horrible crime were these young children.  Hamilton made
his way onto the playground where he fired some more random shots and
eventually committed suicide.  It has become known as the Dunblane
massacre and Hamilton’s exact motives are still not clear.  This attack
remains the single deadliest targeted mass murder of children in the long
history of the United Kingdom.         

Seung-Hui Cho was born in Seoul, South Korea and immigrated to the
United States when he was 8-years-old.  As a child Cho was thought to have
mental illness and was extremely quiet, sinful, and would never physically
embrace anyone.  In high school, Cho was placed in special education
classes under the classification of “emotional disturbance.”  Around 7:15
a.m. on April 16, 2007 Seung-Hui Cho murdered two students in West
Ambler Johnston Hall, a high-rise co-educational dormitory on the campus
of Virginia Tech University.

Two and a half hours later Cho crossed the campus and found Norris Hall.
He put chains on the doors, locked them, and then entered various
classrooms and began shooting and murdering the students and teachers.
He killed 30 people and wounded 25 others in Norris Hall.  The massacre is
the deadliest peacetime shooting incident by a single gunman in United
States history.  It directly led to the passage of the first major federal gun
control measure in more than 13 years.

Seung-Hui Cho was an extremely mentally disturbed and cowardly individual
who decided to take the lives of 32 innocent souls.  After the tragedy, the
national media and many state governments insisted on increasing security
measures in many educational facilities all over the country. 

Jimmy Moody was a British gangster and one of the most feared men of
the last 100 years.  He was the #1 hitman in the world of organized crime
for a long time.  Moody is noted for numerous run-ins with famous
gangsters, including Jack Spot, Billy Hill, "Mad" Frankie Fraser, the Krays,
the Richardsons, and the Provisional IRA.  Moody was the enforcer for
the Richardsons and did deadly freelance work for the Krays.  In the
1970’s Moody and some other organized criminals formed The Chainsaw
Gang, which went on to become one of the most successful and ruthless
armed group of bandits of the era.

After two prison stints Moody decided to become a member of the IRA.
His deadly skills were soon being showcased and he became a secret
deadly assassin for the Provos'.  He was so feared by Northern Ireland
that the Thatcher government put a three-man hit squad on his tail.  There
is no saying how many people he murdered, but his enemy list was
extensive on both sides of the water.  Jimmy Moody was killed in March
1997 at the Royal Hotel in Hackney, East London by an unknown
assailant.  He remains one of the most legendary assassins in English
history.

Simo Häyhä was a Finnish soldier and sniper during the Winter War of 1939,
when the Soviet Union invaded and attacked Finland.  Using only a standard
iron-sighted, bolt action rifle he worked as a sniper and recorded more kills
then any soldier in any other major war.  He was credited with 505 confirmed
deaths.  With temperatures extremely cold and snowy Häyhä would dress in
all white, set a perch, and wait for the enemy to come.  He had many
important skills that helped him become so deadly.  Häyhä preferred to use
iron sights rather than telescopic sights, as they present a smaller target and
aid in concealment.  He would also compact the snow in front of him, so that
it would not be disturbed when he fired a shot.

He would occasionally keep snow in his mouth, so that he would not disturb
his position when breathing.  The Soviet government tried desperately to get
rid of him and ordered counter snipers and artillery strikes in the area.  In
1940, he was shot in the jaw and severely injured during combat, but made it
through the war and was quickly promoted to second lieutenant.  Häyhä
ended up living until age 97.  It should be noted that Simo Häyhä is different
from many of the entries on this list as he was in a war.  His defense and
reckoning was necessary, unlike many murderers on this list. 

Schaefer was raised in Atlanta, Georgia and eventually moved to Fort
Lauderdale, Florida.  As a child he was a peeping tom, had many weird
sexual obsessions, would cross dress, and often kill animals.  He was a
smart man and had an IQ in the range of 130.  In the 1960’s, Schaefer
became a police officer in the state of Florida and went on a killing spree
murdering over thirty young woman and girls.  In July of 1972 Schaefer
picked up two teenage girls in his police cruiser, they were hitchhiking.  He
kidnapped them, took them to some remote woods, and tied them up to two
trees.

He threatened to kill the girls or sell them into prostitution.  However, he
received a call on his police radio and left the scene vowing to return.  The
girls escaped and went to the local police station where they identified the
killer cop.  He was charged with false imprisonment and assault and served
one year in jail.  Sometime later two girl’s bodies were found tied to a tree
and Schaefer was instantly a suspect.  After a search of his home, enough
evidence was found to convict him of the murders.  In 1973, he was found
guilty of murder and sentences to two life sentences.  Twenty-two years later
he was stabbed to death in his cell. 

Shipman was a British general practitioner who graduated from Leeds
School of Medicine in 1970.  He is one of the most prolific known serial
killers in world history and there is evidence to support a total of 218
murders.  In March of 1998 co-workers expressed concerns about the high
death rate of Shipman’s patients.  An investigation found that he was
murdering his patients by administering an overdose of the drug
diamorphine.

He was also signing patients’ death certificates and then forging medical
records indicating that the patients had been in poor health before they died.
This man killed a lot of people and became the only person in British history
to be found guilty of murdering his patients.  It was discovered that over
80% of his victims were elderly woman.  Shipman was sentenced to life in
prison and ended up hanging himself in 2004.

Leibacher was born in Zug, Switzerland in 1944.  He was frequently
unemployed in business, had several failed marriages, and was convicted of
fraud, public obscenity, and obscene acts with children.  He spent some time
in prison and later was diagnosed with a personality disorder and
alcoholism.  He had mental illness and began to believe that he was a target
in a government conspiracy.  On September 27, 2001, which is only sixteen
days after the terrorist attacks on The World Trade Centers, Leibacher
entered the Zug Parliament disguised as a police officer and armed with a
pistol, a pump-action shotgun, and a rifle.

He made his way into the Parliament chamber and began firing randomly into
the room.  Many politicians and journalists were seriously injured.  He fired
around 100 shots killing 14 members of the Zug canton Parliament and
injuring 18 others.  During the attack Leibacher detonated a bomb and then
committed suicide.  It was shocking and the assault was the first of its kind in
Switzerland.  It was truly one of the Canton of Zug’s unhappiest days and
security measures have been changed and upgraded since the massacre.  

Kuklinski was born in the projects of Jersey City, New Jersey.  He had a hard
upbringing and faced metal and physical abuse from his parents.  When he
was very young his older brother was killed by his father.  Richard used to
torture animals as a child and committed his first murder when he was 14-
years-old.  He ambushed a local bully and beat him to death.  By his mid-20’s
Kuklinski earned the reputation of being a dangerous street hustler, who
would fight or kill those who offended him.  During this time he became
associated with the Gambino crime family through local friend Roy DeMeo.

The relationship started when DeMeo ordered Gambino to kill an innocent
man at random, which Kuklinski did.  He became the #1 contract killer for the
biggest crime family in the world.  Richard Kuklinski killed numerous people,
either by gun, strangulation, knife, or poisoning.  He favored the use of
cyanide as it killed quickly and was hard to detect in toxicology tests.
Kuklinski claims to have murdered over 200 men in his lifetime.

He was arrested in 1986 and put on trial for murder under evidence
recovered from undercover agents.  He died in a secure wing at St. Francis
Medical Center in Trenton, New Jersey.  The death has been ruled
suspicious as Richard was set to testify against former Gambino crime
family underboss Sammy Gravano, claiming he ordered him to murder New
York Police Department Detective Peter Calabro.