Dangerous post operative pain!

After any major operation it is usually expected that pain, if any, will subside due to application of anesthesia. But can a patient behave in an unruly manner if his pain becomes unbearable? 

A man, after blaming the doctor, bought an AR -style rifle and went into a shooting spree. He killed the surgeon and three other people before finally shooting himself. 

According to Tulsa police chief Wendell Franklin the killing-patent had back surgery and was in constant pain.