Updated: Oct. 31 at 3:50 p.m.

A part-time professor is in critical condition after he was assaulted near Dupont Circle this weekend.

Jason Chambers, a fencing instructor in the department of exercise science, was dressed in a silver Halloween costume when a man attacked him on S Street near Connecticut Avenue at about 4:20 a.m., according to police records. Chambers suffered a major blow to the head, witnesses told police.

He was “unable to communicate and provide details of the assault” when he was found, according to the police report.

Officers found the 39-year-old “almost motionless” on the sidewalk after the suspect had fled the scene. MPD assigned homicide detectives to the case because of the seriousness of Chambers’ injuries.

He was taken GW Hospital.

Note: A summary of this story in The Hatchet’s email edition incorrectly stated that the crime is being investigated as a homicide. It’s actually being investigated as an assault, though homicide detectives are on the case.