JOINT BASE LEWIS-MCCHORD, Wash. -- The U.S. soldier charged with killing 16 Afghan civilians in one of the worst atrocities of the Afghanistan war pleaded guilty Wednesday and told a military judge "There's not a good reason in this world for why I did the horrible things I did.''

To avoid the death penalty, Robert Bales pleaded guilty to multiple counts of murder. Then, in a clear and steady voice, he described the killings.

Bales, 39, said he left his remote base in southern Afghanistan one night in March 2012 and went to two nearby villages of mud-walled compounds. Once inside, Bales said, he shot each one.

When the judge, Col. Jeffery Nance, asked why he did it, Bales responded: "I've asked that question a million times since then. There's not a good reason in this world for why I did the horrible things I did.''

The massacre prompted such angry protests that the U.S. temporarily halted combat operations in Afghanistan, and it was three weeks before Army investigators could reach the crime scene.

Most of the victims were women and children, and some of the bodies were burned. Relatives have told The Associated Press they are angry at the idea that Bales will escape execution.

The judge still must decide whether to accept the guilty plea.

Bales said he recalled there being a fire and having matches in his pocket when he returned to the base. But he said he didn't remember setting the bodies on fire.

Wednesday's proceedings provided Bales' account for the first time. Last year, survivors testified by video link from Afghanistan and vividly recalled the carnage.

A young girl described hiding behind her father as he was shot to death. Boys told of hiding behind curtains as others begged the soldier to spare them, yelling, "We are children! We are children!'' A man told of being shot in the neck by a gunman "as close as this bottle,'' gesturing to a water bottle on a table in front of him.

Prosecutors say that before dawn on March 11, 2012, Bales slipped away from Camp Belambay in Kandahar Province, armed with a 9 mm pistol and M-4 rifle outfitted with a grenade launcher.

He attacked one village of mud-walled compounds, Alkozai, then returned to the base, woke up a fellow soldier and told him about it. The soldier didn't believe him and went back to sleep. Bales then left to attack a second village, Najiban.

Bales was serving his fourth combat deployment and had an otherwise good if undistinguished military record in a decade-long career. He suffered from post-traumatic stress disorder and a traumatic brain injury, his lawyers say, and he had been drinking contraband alcohol and snorting Valium -- both provided by other soldiers -- the night of the killings.

The case raised questions about the toll multiple deployments take on U.S. troops. For that reason, many legal experts believe it is unlikely Bales would receive the death penalty, as Army prosecutors are seeking. The military justice system hasn't executed anyone since 1961, but five men currently face death sentences.

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