I had the very same experience not long after I adopted my girl, Carly. She had climbed into bed with me while I was asleep and I didn't know she was there. I rolled over and touched her and she jumped up snarling and snapping in my face. Fortunately, she didn't make contact but it scared us both badly. She was in such a panic she fell off the bed. She doesn't get on the bed anymore, but she still has the same reaction if she's startled awake by either noise or a touch after living with me for 6 years. I've accepted that's just how she is and I'm always very careful not to touch her when she may be sleeping. Sometimes it's hard to tell because she often sleeps with her eyes open. You've gotten good advice from everyone else about not letting him on the bed from now on.