Newtown police are asking for help identifying a dirt bike rider accused of causing a serious horseback riding injury on Platts Hill Road. Police say the rider, described as a white male believed to be 13 to 15 years old, sped past two horses on September 1, startling one and throwing its rider to the ground. The woman suffered a broken neck and lost consciousness. Investigators say the rider stopped briefly, apologized, then left the scene.