Mr. Delpeche, 49, was one of two bystanders shot by police officers on Sunday afternoon during a confrontation at the Sutter Avenue subway station between officers and a knife-wielding man who they believed had not paid his fare.

The man who the police said threatened them with a knife, later identified as Derell Mickles, 37, was shot in the stomach. A 26-year-old female bystander was grazed by a bullet and was in stable condition as of Monday. One of the officers was struck by a bullet under his armpit and has been released from the hospital.

Now, Mr. Lee said his friend is barely responsive in Kings County Hospital, where he is in critical condition. Doctors told him that a bullet went through Mr. Delpeche’s head and that fragments were removed. “I’m not sure he can hear me; he did put his thumbs up once,” Mr. Lee said.

The police should not have fired, he said. “It was very reckless of them to be shooting in a crowded train station,” when “they knew a stray bullet could hit someone,” Mr. Lee said. “It happened to be my childhood friend of 30 or 40 years.”