If the Police Officer who assaulted you is a veteran it is possible he left the service sick from a traumatic brain injury and/or PTSD

Traumatic Brain Injury (TBI) is a blow or jolt to the head or a penetrating head injury that disrupts the function of the brain. Each year there are a reported 1.7 million civilian brain injuries in the United States. In the military between 2000 and the first quarter of 2012, more than 244,000 service members sustained a TBI. Brain injury, caused largely by improvised explosive devices (IEDs), has become the signature wound of the wars in Iraq and Afghanistan. Most brain injuries are mild, and most people recover in a matter of weeks. 

Some people do not recover in a matter of weeks and demonstrate symptoms that make them unfit for services that allow them to use force and carry guns.