A gunman opened fire inside a gas station in Missouri late Sunday evening, killing four people including a police officer.

Springfield Police Chief Paul Williams said in a statement on Monday that another officer and citizen were also injured during the rampage.

Police had been notified that a gunman was driving around and shooting at multiple locations around Springfield before crashing into the Kum & Go. gas station and convenience store. At this point, Williams says that the gunman ran inside and began shooting.

The first two officers who arrived at the scene were shot, Time reports.

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When additional officers arrived at the scene they removed the injured officers from the store and found three citizens and the gunman dead. His death appeared to have from been a self-inflicted gunshot wound, according to Williams.

“Officer Christopher Walsh died at a hospital, Williams said. He was with the Springfield police for 3 1/2 years, was an Army veteran and was active in the Army reserves. Officer Josiah Overton, whose injuries are not life-threatening, has been with Springfield police for two years, he said,” Huffington Post reports.

“Both officers showed significant bravery and were heroic in their actions,” Williams said.

The identities of the victims have not yet been made public as the police are still notifying relatives.

So far, the police have not shared a possible motive for the rampage.

“We’re still investigating multiple crime scenes and dealing with grieving the loss of one of our own,” he said.