High-profile mass murder cases

John Allen Muhammad was the mastermind behind the 2002 sniper attacks that killed 10 people in the Washington, D.C., area. Muhammad and his accomplice, Lee Boyd Malvo, were both convicted of a total of seven murders in Maryland and they were also suspected of fatal shootings in Louisiana, Alabama and Arizona. The motive for the shootings in the nation's capital region remains murky. Malvo said Muhammad wanted to use the plot to extort $10 million from the government to set up a camp in Canada where homeless children would be trained as terrorists. But Muhammad's ex-wife has said she believes the attacks were a smoke screen for his plan to kill her and regain custody of their three children. Muhammad and Malvo were captured on Oct. 24, 2002. Muhammad was executed on Nov. 10, 2009 by lethal injection for the killing of Dean Harold Meyers at a gas station in northern Virginia.

Timothy McVeigh - Oklahoma City Bombing

Timothy McVeigh detonated a truck bomb in front of the Alfred P. Murrah Federal Building in Oklahoma City on April 19, 1995. The attack killed 168 people and injured over 800. Before Sept. 11, it was the deadliest act of terror on American soil. McVeigh was convicted of 11 federal offenses and ultimately sentenced to death. He was executed on June 11, 2001.

Tamerlan Tsarnaev and Dzhokhar A. Tsarnaev - Boston Marathon Bombing

AP/The Lowell Sun/Julia Malakie, Bkontakte

Brothers Tamerlan Tsarnaev, 26, left, and Dzhokhar A. Tsarnaev, 19, right, were identified as the suspects in the Boston Marathon bombings that killed three people and wounded more than 180 others on April 15, 2013. Four days later, the FBI enlisted the public's help and released photos and videos of the two young men, who were seen carrying backpacks as they mingled among revelers at the marathon. A few hours later, the brothers engaged in a long night of violence that included allegedly killing an MIT police officer on campus in Cambridge, Mass., stealing a car at gunpoint, injuring a transit officer in a firefight and throwing explosive devices at police during their getaway attempt, authorities said. Tamerlan Tsarnaev, 26, died during the gunfire exchange and Dzhokhar Tsarnaev was apprehended by authorities on April 19, 2013.

Jared Lee Loughner -

Jared Loughner, 22, pleaded guilty in the January 2011 shooting spree that killed six people and wounded more than a dozen others at a campaign event in Tucson hosted by Arizona congresswoman Gabrielle Giffords. Giffords was hospitalized after a bullet passed through the left side of her brain, but survived. On Nov. 8, 2012, Loughner was sentenced to life in prison without the possibility of parole.

Lee Boyd Malvo

Lee Boyd Malvo was the accomplice of John Allen Muhammad in the 2002 sniper attacks that killed 10 people in Washington, D.C. Malvo and Muhammad were both convicted of a total of seven murders in Maryland and both were sentenced to six life terms. They were also suspected of fatal shootings in Louisiana, Alabama and Arizona. The motive for the shootings in the nation's capital region remains murky. Malvo said Muhammad wanted to use the plot to extort $10 million from the government to set up a camp in Canada where homeless children would be trained as terrorists. But Muhammad's ex-wife has said she believes the attacks were a smoke screen for his plan to kill her and regain custody of their three children. Muhammad and Malvo were captured on Oct. 24, 2002. Muhammad was executed on Nov. 10, 2009. The death penalty was ruled out for Malvo because the U.S. Supreme Court barred the execution of juveniles, who was 17 during the killing spree.

James Holmes - Colorado Theatre Shooting

James Holmes, 24, is in custody after allegedly going on a shooting rampage during a midnight showing of "The Dark Knight Rises" at a Century 16 movie theater in Aurora, Colo., on July 20, 2012. Aurora Police said witnesses reported the shooter was wearing a gas mask and released some type of a canister in the dark theater just after the movie began. Officers found the suspect near a car behind the theater and also located a gas mask, rifle, handgun and at least another weapon. This file photo provided by the Arapahoe County Sheriff's Office shows James Holmes, who faces multiple counts of first-degree murder and attempted murder.

Eric Robert Rudolph - Olympic Park Bombing

Eric Robert Rudolph was on the lam for more than six years after perpetrating the 1996 Olympic Park bombing in Atlanta, which killed two people and injured more than 100. Hewas arrested in May 2003 after a N.C. police officer Jeffrey Postell spotted him near a grocery store. In 2005, Rudolph was sentenced to multiple terms of life without parole for the Olympic bombing as well as attacks on women's clinics and a gay bar.