Plot hole: After Ricky has just killed his girlfriend with the car antenna, he's challenged by a police officer. Unless they're very poorly trained, officers would never walk right up to someone who have just committed a murder. Police would always order the suspect into a position that presents the least amount of threat and minimal chance of resistance. Grabbing the officers gun would never had been an option.
Plot hole: The police are on the trail of a known psychotic and mass murderer. When they turn up at the house of the mother superior, it's evident Ricky has been there, as the door has been cut open and kicked in. There is no way the other nun would have been able to freely enter the house without police escort, or even get out of the police car, as Ricky had not been located and apprehended. The house is a potential crime scene and she would not have been allowed in.