Can you kill the Tyrant?
There's a short answer to this question: no. In the immediate period after you first encounter Mr X. there's literally no way to kill the monster, and he's going to follow you around the Raccoon City police station, and the underground parking garage, for quite a while.
How do you beat a Tyrant?
A good way to avoid the Tyrant is by baiting him to throw a punch, then backing off quickly. You'll have enough time to run past him as he recovers from the animation, allowing you to escape. You can also lure him into an open area, where it'll be easier for you to circle around him and go wherever you need to.