They say an officer was on patrol when he saw the muzzle flashes of the weapon being fired.
The officer approached the vehicle and reportedly saw Hayat toss the gun out of the vehicle before running away from the scene.
The victims – Angela Thompson, 55,of Downing Street, Northeast in D.C.; Louie Woodson, 54, of New York Avenue, Northeast in D.C.; and Keith Lee, 54, of no fixed address – were all unresponsive when the officer approached the car.
Police are still trying to determine what prompted the shootings.
Hayat has been charged with three counts of first and second-degree murder. He also faces weapons-related charges.