The incident unfolded in a northeastern Seattle neighbourhood when the suspect approached a motorist at an intersection and shot her before walking into the street and firing on the bus, police said in a statement. (Photo: AP)

Seattle: Two people in Seattle were killed and two others critically injured when a gunman opened fire on two motorists and a Metro bus, then caused a collision as he tried to flee in a stolen car during the afternoon rush hour, police said.

The incident unfolded in a northeastern Seattle neighbourhood when the suspect approached a motorist at an intersection and shot her before walking into the street and firing on the bus, police said in a statement.

The bus driver was struck but managed to turn the bus around and head away from the assailant, police said. The suspect then approached a second motorist, in a Toyota Prius, and opened fire, killing the car’s driver.

As police arrived, the gunman climbed into the Prius and sped away but collided with a nearby vehicle, killing that driver. Officers pursuing the suspect took him into custody following a brief standoff, police said.

Authorities did not immediately offer an explanation for what might have precipitated the shooting or specify the type of weapon used.

The suspect, who was not identified, was taken to a local hospital, where he remained under guard while being treated for non-life-threatening injuries, according to police.

Police said one motorist was killed by gunfire and the other motorist was killed in the collision. Both were men, as was the wounded bus driver. None of the victims was immediately identified.

King County’s Metro transit authority said on Twitter that the bus driver had activated an emergency alarm to report being struck by gunfire, and that none of his 12 passengers was injured.

Although wounded in the torso, the bus driver was able to walk to a gurney to be transported by paramedics to a hospital, the Seattle Times newspaper quoted a transit union president as saying.