We are at war.
We must retrain our minds that we are not sheep to be slaughtered.
First option — unless you are law enforcement or a Soldier — is to escape. Second option is to hide. Final option, kill that son of a bitch. Bum-rush him.
Take his rifle and shoot him in the head.
He might be wearing a vest — when you are very close shoot his head twice and keep moving. If the rifle is out of ammo, kill him with the rifle butt or something else. Smash with all of your strength.
No time for hogtying him. There might be other terrorists and there is no time for pleasantries. Just kill him and keep your weapon pointed at potential enemies. Be very careful not to cause innocent casualties. Can be hard to do.Ugly advice for an ugly age.