Yes, lock him in the basement and call the police. There's no need to get involved with a manslaughter investigation by shooting him. Plus you'll need to clean up all the blood and risk giving yourself something from an accidental exposure. As long as he isn't attacking your gas powered appliances or the door to the rest of the house, let the police deal with him.

Then there's always the tiny chance he's your uncle who's playing a surprise trick on you. Plenty of people have shot relatives or family members thinking they were burglars.