The FBI is reviewing a chilling surveillance video of the Tucson shooting rampage that shows the horrific scene in clear detail, and acts of heroism including federal Judge John Roll being gunned down as he tries to help another man.
The shooting left six people dead and at least 13 others wounded including Arizona Rep. Gabrielle Giffords at a Tucson shopping center.
On the surveillance video, according to people who have seen the tape, Roll, 63, pushes Giffords staffer Ron Barber to the ground in an attempt to get him out of the line of fire. Both men hit the ground. Barber survived his wounds, but Roll, who was shot in the back, did not.
The tapes are in the custody of the FBI and won't likely be released until trial but they vividly show the sequence of events that unfolded the morning of Jan. 8.
The video obtained from the Safeway supermarket shows the area where Giffords was holding a "Congress on Your Corner" event. Authorities said shooting suspect Jared Lee Loughner is seen walking into the picture at 10:10 a.m.
According to officials who have seen the video, Loughner, 22, quickly moves around a table and shoots Congresswoman Giffords in her left forehead, just above her eye.
At the time the shot was fired, Loughner was within three feet of Giffords.
Then Loughner reportedly turned to his left, faced the crowd, and continued the shooting, officials said.
Officials said the crystal-clear video footage shows muzzle flashes as the gun is fired.
Giffords survived the shooting and her condition has been upgraded to serious from critical.
In all, sources said Loughner allegedly fired 32 rounds before he was tackled by participants in Giffords' public event.
"I ran over to him and I knelt down and put my knee in his back, pulled out my cuffs and handcuffed him in place right there," said Pima County Sheriff Deputy Thomas Audetat. "As far as my recollection goes, he did not struggle with us at all."
Since his arrest, sources have described Loughner as calm, detached, and often smiling.
Loughner appeared in federal court on Jan. 10 and faces several federal charges including one count of attempted assassination of a Congress member, two counts of killing an employee of the United States and two counts of intent to kill employees of the United States.
He could be sentenced to death or life in prison if he is convicted of murdering either federal employee.
The tapes may provide additional evidence that the assault was pre-meditated.
Loughner reportedly had ear plugs and was seen on tape talking calmly to a Safeway clerk in the moments before the shooting.
Sources said his parents have cooperated with the investigation and apparently had no idea what he had been planning.
ABC News' Leezel Tanglao contributed to this report.