FORT COLLINS, Colo. (KDVR) — A 35-year-old man who allegedly assaulted an undercover Fort Collins Police Services detective at the end of last month is facing a second-degree assault charge.

The Larimer County Sheriff’s Office said Quentin Wallace, of Loveland, was not charged with assaulting a police officer as evidence showed he did not know the man he struck was law enforcement. Wallace was arrested on Thursday and booked into Larimer County Jail.

Cop struck, seriously injured during undercover operation

According to LCSO, undercover Fort Collins Police Services detectives in plainclothes were conducting follow-up work related to a previous case.

While they were in Loveland, they were approached by Wallace, an acquaintance of the suspect in that case. Wallace allegedly confronted and ultimately struck one of the detectives, who suffered serious injuries. The detective was transported to an area hospital and is expected to recover.

That detective remains in the hospital in critical condition, LCSO said.

The Critical Incident Response Team was activated due to the seriousness of the detective’s injuries.

Wallace was detained and interviewed by CIRT detectives at the Loveland Police Department, then was released pending further investigation.

The District Attorney’s Office accepted charges against Wallace and the CIRT investigation continues.