Wow, this is a sad story. Ideally, you did the right thing, but at what cost? I sincerely hope that you have recovered from the guilt, and that you don't carry it around anymore because we all have made mistakes like these. Far worse than this. At least deep down, you know you didn't have the intention to hurt him.
Hopefully you can rest in knowledge that what you did, anyone in your position would do the same thing. Thankfully he wasn't expelled. As for him not trusting you anymore, It is what it is, cut your losses and move on. You'll find even more meaningful friendships in the long run.
