Two San Diego firefighters were listed in stable condition at a hospital, a day after a bystander stabbed them multiple times as they were helping a man with a medical problem in the downtown area.

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 a trolley platform, said Lee Swanson, spokesman of the San Diego Fire-Rescue Department.

Police and other firefighters rushed to the scene and authorities arrested a suspect. 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, The San Diego Union-Tribune reported Thursday (http://bit.ly/1GKQztr ).

One firefighter was stabbed in the back and both were stabbed more than once, Swanson said. He 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 newspaper.

The names of the firefighters have not been released.