But the assassin had already talked to Gifford. As his friend twittered today: "He was a political radical & met Giffords once before in '07, asked her a question & he told me she was 'stupid & unintelligent.'"
He was aiming for Gifford; Roll was "collateral damage":
Another chilling twist was the presence of John Roll, a district judge, among the dead. He and his family were given protection in 2009 after he ruled that a lawsuit by illegal immigrants could proceed – a decision that was denounced on conservative talk show radio and brought an estimated 200 death threats.
The shooting took place in a car park outside a Safeway grocery store in a Tucson shopping mall as Miss Giffords was talking to an elderly couple at a "Congress on your Corner" event which she had advertised an hour previously on her Twitter account.
Andrea Gooden, an eyewitness who was working across the road from the shooting, said: "I heard about 15 shots. Then there were people racing across the parking lot."
Steven Rayle, who was on the scene at the time of the shooting and helped to hold the suspect down while waiting for police, told the Gawker website: "The event was very informal. Giffords had set up a table outside the Safeway and about 20 to 30 people were gathered to talk to her. The gunman, who may have come from inside the Safeway, walked up and shot Giffords in the head first."
Alex Villec, 19, a campaign volunteer, was organising the line of constituents when the shooter first approached.
The gunman "said, 'Can I talk to the congresswoman?', or something to that effect," said Mr Villec, who told him to join the queue.
A few minutes later, the man left the back of the line and walked toward Miss Giffords amid a group of 20 to 25 constituents, employees and volunteers.
"He was intent when he came back - a pretty stone-cold glance and glare," Mr Villec said. "I didn't see his gun, but it was clear who he was going for. He was going for the congresswoman. A few staff members were caught in the crossfire...His goal was the congresswoman."
Mr Villec saw him raise his hand and heard gun shots before ducking behind a pillar and later running across the car park to a bank for safety.