HOUSTON (KTRK) -- A Houston police mounted patrol horse had to be put down following an accident in downtown Houston Thursday morning.At about 10:15am, a mounted patrol officer was headed southbound on Fannin, just north of Congress. The officer was traveling in front of a concrete truck headed the same direction when something spooked the horse, and the animal backed up into the truck.The horse suffered severe injuries to its hind legs and had to be euthanized at the scene.The officer on the horse was not seriously injured, and was taken to a hospital for evaluation.