SAN DIEGO (AP) – Two San Diego firefighters were hospitalized with multiple stab wounds but one of them was expected to go home Thursday night, a day after a bystander attacked them as they were helping a drunken man on a packed trolley platform.

The attacker approached the firefighters at about 4 p.m. Wednesday as they were responding to a 911 call reporting an intoxicated man had become ill on the downtown platform, Capt. Joe Amador of the San Diego Fire-Rescue Department said.

“As you can imagine, it was chaos,” Amador said. “There were multitudes of people on the platform at the time.”

Police and other firefighters rushed to the scene and authorities arrested a suspect. One firefighter was stabbed in the back and both were stabbed more than once, The San Diego Union-Tribune reported.

Ben Vernon, 32, was the more seriously injured and had several stab wounds to his torso and a punctured lung, officials said.

Alex Walbertt, 37, also had multiple wounds to his torso but was expected to be released from the hospital sometime Thursday night.

Their alleged attacker, Ryan Allen Jones, 34, was being held in county jail without bail and faces charges of attempted murder, assault with a deadly weapon and resisting arrest, according to the newspaper.

Police were trying to determine a motive.

Fire department spokesman Lee Swanson said he did not know if the firefighters exchanged words with the assailant before the attack.

“My understanding was he just came upon them,” Swanson told the Union-Tribune.