Pima County Sheriff’s Chief Rick Kastigar said he watched the first part of the surveillance video, which shows 22-year-old Jared Loughner shooting Giffords in the forehead from about 2 feet away. It also shows U.S. District Judge John Roll trying to shield Giffords aide Ron Barber from gunfire.

“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.”

Roll was shot in the back; he and five others died from their injuries. Barber was among 13 people shot and wounded.

The 22-year-old gunman had been bent on targeting Giffords since meeting her at a 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 Roll and 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.

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

“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 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 the southern Arizona desert city.

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.”

Inside the hospital, Giffords’ husband, Mark Kelly, has been keeping his own vigil. He told ABC’s Diane Sawyer in an interview that aired Tuesday night that he believed for about 20 minutes that his wife was dead after seeing a mistaken television news report.

Kelly, an astronaut, said he had rushed aboard a friend’s plane to fly to Arizona after hearing of the shooting.

“I just, you know, walked into the bathroom, and you know, broke down,” he said. “To hear that she died is just, it’s devastating for me.”

Kelly said he later learned that she was alive when he called Giffords’ mother, who was outside the operating room.

Giffords isn’t aware that six people died in the shooting, including Gabe Zimmerman, one of her staff members, Kelly said.

Kelly told Sawyer that he was sure Giffords recognizes him at her hospital bed, since she has continued with a habit of playing with his wedding ring — moving it up and down his finger and sometimes putting it on her thumb.

“She’s done that before,” he said. “She’ll do that if we’re sitting in a restaurant. She’ll do the same exact movements.”