The former Marine fired his M-16 alongside his squad leader, shooting off round after round into the dark bedroom of the Iraqi home, fearing he was under attack. But he admits he only saw silhouettes, some small, and he only heard his own squad's gunfire.

Later former Cpl. Stephen Tatum discovered he and Staff Sgt. Frank Wuterich had killed a woman and children in the back bedroom of the home during a series of raids near where a roadside bomb exploded shortly beforehand, killing a Marine.

Still, Tatum said to this day — six years after the incident in the town of Haditha — he does not believe his squad did anything wrong.

Tatum gave his account Tuesday during the second day of testimony in the trial of Wuterich, the last defendant in one of the biggest criminal cases against U.S. troops to emerge from the war, which was declared over in December. Other squad mates are expected to take the stand during the trial this month, but it is not known which day that will happen.

Wuterich faces nine counts of manslaughter and other charges after prosecutors implicated in the deaths of 19 of 24 Iraqis killed that day. One squad member was acquitted. Six others, including Tatum, had their cases dropped.

The tragedy prompted tightening of combat rules, with commanders demanding their troops positively identify their targets before firing.

Defense attorneys say Wuterich believed insurgents were hiding in the homes after the roadside bomb exploded near their convoy, killing Lance Cpl. Miguel Terrazas and injuring two others.

Tatum said he shared that fear because immediately after the bomb the Marines came under small arms fire. But he said he did not know where the gunfire originated. Wuterich and another Marine fatally shot five Iraqis outside a white car near the scene then headed toward the closest home, Tatum said.

Tatum acknowledged that charges against him were dismissed in exchange for testifying.

He told military prosecutors that squad members tossed grenades and shot rounds into rooms of two Iraqi homes for 45 minutes in the wake of the bombing that killed Lance Cpl. Miguel Terrazas and injured two others. But he said they did not take any gunfire during that time nor find any weapons or insurgents.

Following his squad leader, Tatum said the Marines edged along walls with their weapons drawn. They tossed fragmented grenades into rooms. In a back room of the first home, Tatum said he joined Wuterich in firing rounds but was unable to see what he was shooting at because of the darkness and flying debris.

"I saw silhouettes of targets and that was really it," Tatum said, adding that it looked like there was a man standing or kneeling.

Then someone yelled a person had fled. The Marines rushed out to a neighboring house, tossing in grenades and shooting off rounds there as well. Tatum saw the body of an Iraqi man near the kitchen when he went in after his fellow troops.

While checking an empty room, Tatum said he heard movements in a back bedroom and then Wuterich firing his M-16. He went in to assist Wuterich, shooting at what he said were silhouettes, some big, some small.

"The only thing that gave me any indication there was a hostile act in there would be Staff Sgt. Wuterich firing sir," Tatum told military prosecutor Lt. Col. Sean Sullivan.

Wuterich also acknowledged that he did not positively identify his targets, three investigators testified.

Tatum returned later when the house had been determined to be safe and learned they had killed an unarmed woman and children in the room.

Staff Sgt. Justin Laughner also went in after the raids to gather military intelligence and testified Tuesday that he found no signs of insurgents. He took photographs of 23 bodies.

In 2008 testimony in the court-martial of another Marine in the case, Laughner acknowledged deleting photos he took at the scene under an officer's orders and later lied repeatedly to investigators about what happened to the images.

"I remember some of the kids had their eyes open," Laughner testified Tuesday, saying he was shaken by the carnage he saw in the back bedroom.

"I just wanted to leave the bedroom," he said. "I just thought it was really sad."

Prosecutors have painted a picture of a young Marine with no prior combat experience losing control after seeing his friend's body blown apart.

Wuterich has said he regretted the loss of civilian lives but believed he was operating within military combat rules.

Wuterich listened Tuesday, occasionally rubbing his chin and whispering in the ear of his attorney during the day's testimony.

Defense attorney Neal Puckett suggested Tatum had changed details of his account since talking to investigators. Tatum said mistakes could have been made in the investigating reports but he stood by his testimony.