The unidentified Southfield, Mich., man was working for an heating and air-conditioning company at a job site in Birmingham this week when his .40-caliber Glock pistol went off accidentally.
Deputy Police Chief Mark Clemence told the Detroit Free Press the worker had a permit for the weapon, but the city prosecutor was going to review the matter.
Despite the possibility of criminal charges, Clemence told the newspaper the outcome could have been worse for the victim, who was taken to the hospital by a co-worker.
"Your femoral artery runs down there," Clemence said. "It could have been a lot worse. It's a big bullet; you're not talking a small bullet."