Since police won’t give us a motive, lets come up with our own.
What I think is most likely:
Guy up for days on meth who thought people were trying to kill him. Loaded up his car with guns and took off to get away from the people he thought were trying to kill him. Gets pulled over by police, thinks they are going to kill him, so shoots the cop and takes off, killing everyone he sees along the way in his meth induced psychosis.
Less probable but more interesting:
Guy was on his way to commit a mass shooting at the theater when he was pulled over. Guy decides his original plan is going to be stopped by the police so he shoots the cop and heads to theater killing as many people as he can along the way.
Ex-con got pulled over. Had guns and drugs. Realized he’s going back to jail. Said “fuck it”. Shoots cop. Shoots at a bunch of cars in his way. Steals USPS truck. Shoots at businesses along the strip. Heads toward movie theater. Gets shot up and BTFO by cops. The end.
The only motive was he was a criminal illegally owning a gun and in possession of drugs and was going to go back to jail and didn’t want to.
Criminal with a gun. Probably a Democrat. They will use his illegal operation of a firearm to demand that all law abiding gun owners surrender their weapons as usual.
I think it could have been the result of a foiled terrorist attack. Our police always try to keep that information under wraps if they can, so as to not frighten the horses.