No information was given on whether the civilian hit the suspect.
Acker said the suspect, identified only as a 49-year-old white man, was undergoing treatment Friday evening at a hospital in Youngstown for life-threatening injuries.
The man was wounded in an exchange of gunfire with police shortly after midnight outside a convenience store in Farrell. The incident began when a Farrell police officer encountered the man and determined that the man, who has not been named, was carrying a weapon.
After the man was wounded, he still refused to surrender the weapon. Acker said the police officer also fired bean-bag rounds during the incident, and police used an armored personnel carrier provided by Mercer County Critical Incident Response Team to disarm the man.