English class had let out and Oswaldo Fajardo, 39, was standing in a parking lot talking to a female classmate when a man ran up and stabbed him, reported Santa Rosa police on Wednesday.
The attacker was the woman's husband, said Santa Rosa police Sgt. David Linscomb.
Fajardo of Santa Rosa remained hospitalized Wednesday with a severe stomach wound.
Officers late Tuesday night arrested Miguel Ascencio, 35, of Santa Rosa, suspecting he was trying to kill Fajardo.
The motive remained under investigation. The couple reportedly had been having relationship issues, Linscomb said.
"There doesn't appear to be any previous issues between the husband and the victim. It seems like they didn't even know each other," said Linscomb.
Fajardo and the woman were classmates in the Tuesday night English class at the Santa Rosa Junior College satellite center on South Wright Road.
Class had let out and as the two walked to their cars they stopped to talk.
"(Ascencio) appeared out of nowhere," Linscomb said.
Driving his car, the man sped up to the two, got out, stabbed the man and ran from the parking lot, said Linscomb.