They don't need to. Fleeing the scene after shots were fired from that car, wounding a person? [While perhaps only confirmed after the fact, the guns in the car show that it was the right car.] That's a solid case of a fleeing felon who can reasonably be presumed to pose a risk to others.
Tennessee v. Garner, 471 U.S. 1.
A police officer may not seize an unarmed, nondangerous suspect by shooting him dead...however...Where the officer has probable cause to believe that the suspect poses a threat of serious physical harm, either to the officer or to others, it is not constitutionally unreasonable to prevent escape by using deadly force.
Justice Byron White
Are you sure that this car was the suspect car?
If so, why?