Police were called to Tower 1 early Monday after a fire alarm went off. Arriving officers found a man dead from what appeared to be a self-inflicted gunshot wound.
Police told local TV stations they found an assault weapon and improvised explosive devices on the scene.
It was not immediately known whether the dead man is a student.
About 500 students were evacuated from the dorm to the student union, and a parking garage was closed.
The university has cancelled classes through noon Monday as a precaution.
"It's unnerving, for sure," one young woman told CBS Affiliate WKMG. "Definitely not used to it, especially living on campus. You hear about that a lot living off campus, but it's especially rare living on campus."
A statement on the university's website said the UCF Arena will open Monday morning to accommodate displaced students.