A police officer was killed, and three officers were wounded when a gunman opened fire aboard a commuter bus near Denver Thursday night, authorities said. 

Police officers responded to a call about a man who was believed to have been involved in a hit-and-run incident earlier on Thursday, the New York Times reported. 

The officers found the man boarding a Regional Transportation District Bus at an intersection in Lakewood, Colorado, a suburb in the western part of the Denver metropolitan area. 

As police followed the man on the bus, he opened fire on officers, John Romero, a spokesman for the Lakewood Police Department, said in a news briefing. 

Four officers and a civilian were shot. The officers returned fire and killed the gunman, according to Romeo. 

The Lakewood Police Department has not identified the gunman, only saying he was an adult male.