A police officer was on Sunday shot dead in front of a police station.

The officer, Jacai Colson, 28, was shot dead when a gunman opened fire on a police station in the Maryland suburbs of Washington, D.C.

Police authorities said the attack was unprovoked.

A reuters report indicated that the assailant and a second suspect were arrested hours after the incident.

“The accused gunman was wounded in the ensuing shootout with several officers outside the station but was expected to survive,” Prince George's County Police Chief Henry Stawinski told reporters hours later.

The second suspect, who was believed to have accompanied the shooter but fled the scene when the gunfire began, was taken into custody about 30 minutes later following a search of the area, Stawinski said.

"It wasn't about anything," Stawinski told reporters at a news conference outside the hospital where the slain undercover officer, Jacai Colson, was declared dead. Colson, a four-year veteran of the force, had been rushed to the hospital by a fellow officer in the back of a squad car.

"This man launched an attack on a police station and engaged several Prince George's County police officers in a gunfight, to which they responded heroically," Stawinski said.

He called the late-afternoon attack unprovoked, adding: "My understanding is he opened fire on the first officer he saw and then continued that conduct as officers became aware of what was going on, and then several officers engaged him."

*Photo shows late officerJacai Colson.