The American soldier accused of killing 16 Afghan villagers in a shooting rampage is sitting in a military courtroom for the next week or more, hearing the evidence against him.

The Article 32 hearing began Monday at Joint Base Lewis-McChord in Washington state to determine if a trial is warranted for U.S. Army Staff Sgt. Robert Bales, who could get the death penalty if convicted.

The deadly shooting spree near a small U.S. base in Afghanistan's Kandahar province last March strained already tense U.S.-Afghan relations and intensified a debate about whether to pull out American troops ahead of their planned 2014 withdrawal.

"He committed a mass killing crime, and we would like the court in the United States to implement justice and punish him according to the crime," Ahmad Zia Syamak, a spokesman for Afghan President Hamid Karzai, told CNN on Monday.

Bales acted with "chilling premeditation" and was "lucid, coherent and responsive" when he left the remote outpost and went from house to house, gunning down villagers, Lt. Col. Joseph Morse, the Army's prosecutor, told the court. Women and children were among the 16 dead and six wounded, authorities said.

"Nothing really justifies killing women and children in a noncombat situation," Bales' attorney, John Henry Browne, told CNN earlier. "But there may be explanations if that's true."

The first soldier to testify Monday was Cpl. David Godwin, who said he watched a movie and drank Jack Daniels whiskey with Bales and another soldier, Sgt. Jason McLaughlin, just hours before the alleged attack.

The soldiers drank moderately and did not get drunk, Godwin said.

Godwin was awakened early the next morning and told Bales was missing from camp, he testified. The soldiers searched the camp for Bales, who re-appeared about 4:30 a.m. and was taken into custody, he said.

Sgt. McLaughlin testified next, telling the court that Bales had awakened him at 2 a.m. and told him he had been in a nearby village and had "shot some people up."

Mclaughlin said he didn't believe Bales and he told him to let him get back to sleep because he had to go on duty in an hour.

"I'll be back at 5," he said Bales told him. "You got me?" As Bales departed, he told McLaughlin, "Take care of my kids," McLaughlin testified.

When Bales approached McLaughlin and Godwin after he was taken into custody he asked them "Did you rat me out? Did you rat me out, man?" Godwin testified.

Bales, who had blood on his uniform and face, said, "I thought I was doing the right thing," Godwin testified.

While waiting for helicopter to take him away, Bales told Godwin "It's bad. It's bad. It's real bad," Godwin said.

Capt. Daniel Fields, the third witness, said that when he asked Bales what had happened after he surrendered, he replied, "I'm sorry I let you down."

A crowd of Afghan villagers gathered outside the camp as the sun began to rise that morning, Fields said. He was told their trucks were filled with people who had been shot, he said.

"Interpreters were spit on because the people knew they worked for Americans," so the U.S. soldiers stayed out of sight to avoid a confrontation, he testified.

Browne said in a CBS interview that his client appeared to have memory problems predating the incident.

"He has some memories about what happened before the alleged event and some memories after the alleged event and some windows here and there into things, but he really doesn't have any memory," Browne said.