arizona police chief terry rozema has voiced his support for his officer after dashcam footage emerged .
officer michael rapiejko is seen mounting a sidewalk in his speeding police car and knocking down armed suspect mario valencia .
pozema argued that rapiejko may actually have saved valencia 's life because we do n't know what he would have done next .
` we do n't know that if -lrb- rapiejko -rrb- lets him go for another 10 seconds , -lrb- valencia -rrb- does n't take somebody out in the parking lot , ' rozema said .