The two men began fighting shortly before 5:30 p.m. Wednesday on Turk Street near Jones Street, and one of them stabbed the other.

The victim, identified as Darnell Curry, 31, crossed Jones Street to where an ambulance was parked for an unrelated call, police said. He was taken to San Francisco General Hospital, where he was pronounced dead.

In reviewing surveillance video from a cell-phone store and a Salvation Army outlet, police saw the stabbing and the assailant running away, investigators said. Plainclothes officers found a man with a bloody knife who matched the attacker's description, police said.

Inspector Dennis Maffei said the man who was arrested, Tommy Thomas, 63, has an extensive criminal history.

"He claimed it was self-defense," Maffei said. "But his history is very long, very violent, including a couple of attempted murders and some violent sexual offenses."

Thomas was pushing wheelchair at the time of the fight, Maffei said.

"There was a lot of back-and-forth stuff," the inspector said. "The victim grabbed a plastic advertising frame and threw it at the suspect. He was stabbed shortly after that."

E-mail the writers at hlee@sfchronicle.com and jvanderbeken@sfchronicle.com.