Five people including a police officer and a gunman have died in a shooting at a petrol station in the United States state of Missouri after the attacker went inside and opened fire, police said on Monday.

The dead also includes three citizens, Police Chief Paul Williams announced on Monday. An officer was injured along with another citizen.

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Williams said police received reports of "multiple shooting calls throughout the city" late on Sunday. As officers responded, witnesses reported a vehicle crashed into a Kum & Go petrol station and convenience store, and the armed attacker ran inside and began shooting at customers and employees, Williams said. The first two officers who arrived were shot.

Other officers pulled the injured officers from the store and then went inside, where they found three citizens dead. The gunman was also found dead, apparently as a result of a self-inflicted gunshot, Williams said.

Officer Christopher Walsh died at a hospital, Williams said. He was with the Springfield police for more than three 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.

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

The identifies of the other victims have not been released pending notification of relatives.

Police are still working to determine a motive for the shooting, the chief said.

He said it was too early to comment on the effects the shooting had on his department.

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