March 16 (UPI) -- Four people, including a police officer, were killed Sunday night by a gunman in Springfield, Mo., authorities said Monday.
Springfield Police Chief Paul Williams said three of the four were shot dead in a 20-minute shootout at a convenience store. The gunman also killed himself.
Williams said the slain officer, identified as Christopher Walsh, was among the first to arrive at the store and was immediately fired upon by the shooter. The injuries to the other officer are not life threatening, the chief said.
Authorities are not yet sure about a motive.
"Officers throughout Missouri protect us every day without hesitation & without second guessing the potential impacts on themselves," Missouri Gov. Mike Parson teeted. "They do a job that most don't want to do, but expect them to. It's our responsibility to pay tribute to them with the highest respect."
Springfield is located about 180 miles southwest of St. Louis.