The guy he shot wasn't a cop. It was hotel security, and he would have known that from the cameras.
At that point, local cops were working floor to floor with the elevators shut down. Once SWAT arrived, they entered his room. It had been quiet for some time.
What tinfoil said is plausible, as there is not one person close to this who has spoken who believes this man had the ability to organize this, including the sheriff and every military analyst who says from a military perspective that this was the work of a trained specialist TEAM