Sacramento - Spencer Stone, the US Air Force airman who helped thwart an August train attack in France, was trying to stop a fight between a man and a woman outside a Sacramento, California bar when he was stabbed, a witness told a local TV station.
Stone remained in hospital in serious condition on Friday at UC Davis Medical Centre in Sacramento after undergoing surgery on Thursday. The hospital said he was expected to make a full recovery.
Eric Cain, who works at a liquor store near the bar and witnessed the fight, told the CBS Sacramento affiliate KOVR on Thursday that a woman was arguing outside the bar with a man who appeared to be her boyfriend. She hit him with a plastic bag and he then punched her in the face, Cain said.
"The big dude, the white guy, stood up and kinda got in his face," Cain said, referring to Stone.
Stone was stabbed several times in his torso during he fight, authorities said.
"I saw the back of his shirt. I saw a big red mark on the back of his shirt and another random person walked by, and I just kinda went, 'I think the dude got stabbed,'" he said.
Stone was one of three Americans who subdued a gunman on a train headed to Paris in August.
Authorities said on Thursday's stabbing was not related to Stone's role in the train incident and had no connection to terrorism.
Stone's assailant has not been caught.