A Minneapolis man brutally attacked a 75-year-old man who asked that he and his friends lower their voices on a Metro Transit bus, according to charges filed Friday.

Leroy Davis-Miles, 23, was charged with felony assault in the Wednesday afternoon attack that left the victim in grave condition. The victim suffered a critical brain injury and is not expected to survive.

Authorities used facial recognition software to track down Davis-Miles from surveillance footage that captured the incident.

According to the criminal complaint, the 75-year-old man boarded the bus shortly before Davis-Miles and a group of his friends. During the ride, cameras overhead captured the victim approaching the group asking them to stop being loud. The young men responded by becoming hostile and threatening to beat the man when he got off the bus.

A short time later, the group followed the older man as he exited at the Chicago-Lake Transit Center. Surveillance video and witnesses told police that Davis-Miles walked parallel to the victim on the sidewalk before walking up and punching him once.

The man was knocked backward, and he struck his head on the pavement.

Davis-Miles shook hands “in a congratulatory manner” with one of his friends as the man lay unconscious on the ground, charges say. Then several of them rummaged through his pockets.

Footage from the bus and transit center offered several different angles of the suspect, and police were able to identify him. A search of his home located the same jacket, pants and shoes that officers observed him wearing in the video, the complaint said.

Davis-Miles has previous convictions for drugs, domestic assault, terroristic threats and theft. He remains in the Hennepin County jail ahead of his first court appearance on Tuesday.

More serious charges are pending should the victim die.