Police said the attack began when the teenager demanded the 46-year-old victim's wallet while walking on a street in Whittier about 9:15 p.m. Saturday. The man allegedly refused and a fight ensued.
Police said 51-year-old Richard Aragon, the dog's owner, was walking Rocky when he saw the fight and let the pit bull loose.
The victim had the tips of his ears bitten off, injuries to his face and required 10 stitches to close a gash in the back of his head. He was in stable condition at an Orange County hospital.
After the fight, police found Aragon and his 16-year-old son in a nearby apartment complex. They were taken into custody and booked for attempted robbery and assault with a deadly weapon.
Daniel Cramer, a friend who was walking with the boy at the time, said he believes the man misunderstood what he was asking for.
"We were just walking. He tried asking some guy for a cigarette and then that guy took it in the wrong way," Cramer said.
Police aren't buying it.
"No, it was a robbery," said Officer Jessi Pollnow of the Whitter Police Department. "The male juvenile suspect approached him and demanded his wallet."
The teenager's mother, Kimberley Flores, said she doesn't believe Aragon or her son were involved in an attempted robbery.
"Any normal father, if they see their child in a fight with someone, they're going to want to go and intervene. He's not going to turn his back and walk away," she said.
The black pit bull was in quarantine for 10 days.
Court records show Aragon has a criminal past, including a conviction for spousal battery in 2001 and disturbing the peace or provoking a fight in 2000.