op, he should've never had the chance to run out the door.
also, he might not 'know you're alpha' what does that mean in your interpretation?
If he is going to be penned or crated all day in the event that somebody comes to the door, that IMO is just as bad as being sheltered.
Besides being professionally trained, I work with him all of the time. Incidentally, I have walked the dog past the teen that he attacked many times before the attack. In his mind I guess that when he is walking with me, he has a job to do and that is to stay tight to me, look forward and walk.