TUCSON — The chief investigator for the sheriff’s department here has for the first time publicly described the brief and gory video clip from a store security camera that shows a gunman not only shooting Representative Gabrielle Giffords just above the eyebrow at a range of three feet, but then using his 9-millimeter pistol to gun down others near her at a similarly close range.

The video, according to Richard Kastigar, the investigative and operational bureau chief of the Pima County Sheriff’s Department, also reveals that Judge John M. Roll appears to have died while helping to save the life of Ronald Barber, a Giffords employee. Mr. Barber, who was near Ms. Giffords when he was shot twice, has left the hospital.

Mr. Kastigar said Tuesday that the video shows Ms. Giffords standing with her back a few inches from a wall when she was shot by the gunman, who approached in “a hurried fashion” with the gun at his side and then raised it and fired a single bullet above her eye at a range of no more than two or three feet.

Jared L. Loughner, 22, has been arrested in the shootings. In the video, the pistol “is down near his right side, but it is visibly out from where he was keeping it, presumably under his clothing, and then he raises it and fires,” Mr. Kastigar said. “It happens in a matter of seconds.”