kyle90 might want to check state laws before he catches someone in his house. In most states his actions would get him charged with manslaughter unless he reasonably believed his life to be in danger. Texas and a couple other states might be more lenient.
If I caught someone stealing my bike, I would approach them in my butchest manner and demand they unhand it. I bet they would too. If they didn't, I'd grab the bike from them. If they fought back, I would defend myself the best I could with no worries if I damaged them. In my mind that would be the moral thing to do, and I believe the law would back me up.
Always keep your bike locked. Before you fight for it, make sure it is your bike. I heard about somebody who shot a guy stealing his car, only to find out it wasn't his car--just the same model and color. OOPS!