Officer B.K. Hardin of the Knoxville (TN) Police Department was directing traffic on a Saturday in late November when an unknown assailant ambushed him with a strike to the head with a blunt object—possibly a hammer or tire iron—severely injuring him.

According to WBIR News, the 51-year-old officer said at a news conference on Friday that he is recovering well, and hopes to soon return to full duty, but remains frustrated that he cannot help investigators identify his attacker.

"I didn't see him and I think that's the toughest thing for me to deal with," Hardin said. "I want to know what my suspect looks like, where he may be. Not being able to give any details to investigators has been frustrating on my side of it."

Hardin also spoke about the suddenness of the attack, saying that in one instant he was helping pedestrians to safely navigate through traffic, and in the next he was just trying to stay upright.

"The world started spinning," he remembered.

An off-duty firefighter from another county happened to be nearby with medical supplies on hand. He treated Hardin until the officer was transported to a nearby hospital where he underwent surgery. Hardin was released from the hospital two days later.

He has been dealing with concussion symptoms since his injury, but is optimistic that he will make a full recovery.

The Fraternal Order of Police has offered a $5,400 reward for information leading to the arrest and conviction of the person responsible. The TBI has offered $2,500. An anonymous community member from Oak Ridge pledged an additional $5,000. The total reward is now up to $23,400.