Surveillance video from a Tucson Safeway shows moments of mayhem and heroism as a gunman shoots U.S. Rep. Gabrielle Giffords in the face, then turns the gun on a crowd of people waiting to meet her, a Pima County Sheriff's Department official said Wednesday.

Pima County Sheriff's Chief Rick Kastigar said he watched the first part of the surveillance video, which shows 22-year-old Jared Loughner walking around a folding table behind Giffords, going up to her and shooting her in the forehead.

"He didn't run but he very purposefully and rapidly walked around that table and directly up to her," Kastigar said, estimating that the shooter was between 2 and 2.5 feet away from Giffords when he fired. "That was the first shot, and it was fired very quickly and very deliberately at her."

The 22-year-old gunman had been bent on targeting Giffords since meeting her at similar event in 2007, authorities said. She is in serious condition after the bullet traveled the length of her brain.

The video shows Loughner turning toward a group of people sitting in chairs, then stepping out of view. Kastigar said that's when Loughner indiscriminately fired at the seated group and turned toward U.S. District Judge John Roll and Giffords aide Ron Barber.

Kastigar said Loughner shot Barber, and almost simultaneously Roll moved Barber toward the ground and both crawled beneath the table, with Roll getting on top of Barber in an apparent effort to shield him.

Roll was then shot in the back; he and five others died from their injuries. Thirteen people were wounded.

"I believe the judge is a hero," Kastigar said. "I think Judge Roll is responsible for directing Mr. Barber out of the line of fire and helped save his life."

Barber was shot in the leg and in the face and neck area and survived.

"You know, I've been a cop for three decades and I've seen some pretty traumatic and disturbing things, and this was very, very upsetting to watch this," Kastigar said of the video.

The sheriff's office turned the video over to the FBI, which has declined to release it.

The Jan. 8 shooting rocked Tucson and the nation, resulting in an outpouring of support for Giffords and the other victims, including thousands of candles, cards, balloons and bouquets across Tucson.

Bicycle riders gathered Tuesday evening for a 2-mile vigil ride from the hospital to honor Giffords, an avid cyclist.

"This gives us an opportunity to share and do something positive. What happened was awful," organizer Damion Alexander said. "It's so sad. And whenever something bad happens, you have an opportunity to be brought down by it or to look at how you can lift up the spirits and make it a better place to live."