Parenting Dilemma

For the past few months we've been dealing with Bear's anger.  He is almost three, and the kid has a temper.  As he has gotten more verbal he has gotten much better at controlling his temper and expressing himself.  He does have a tendency, however, to  hit Wild Man or me.  As an aside, Bear rarely hits Archer, and the only explanation I have for this is that at 6'2", Archer is much bigger than Bear.  Bear hits under fairly normal circumstance--when he and Wild Man are squabbling over a toy, when I'm disciplining him, or when he is unable to express himself.  As I've said, he has improved a lot in the past 4 months or so, primarily because we've been firm.  At times, I've been firmer than I'd like to be, but honestly, Bear responds to firmness in a way that Wild Man did not.  We were at a point when I thought we had almost moved past this stage. 

Recently though Bear has regressed a bit.  A few times a week he will walk up to me or to Wild Man and just hit us for no real reason.  Archer and I were both at a loss for this behavior.  We continued our normal discipline tactics, but it didn't really seem to work.  This morning I witnessed something that explains the behavior.

At daycare this morning, Bear was unusually fussy.  He has never handled drop offs particularly well, although he is generally fine less than two minutes after we leave his classroom.  This morning he was out of sorts because Archer's schedule necessitated that we took him to his classroom by 8:30, which means that we were out of the house a bit earlier than usual and that I was the only parent dropping off.  Any change can throw Bear off, whereas Wild Man adapts much easier.  Because he was upset, I spent more time with Bear.  As I was finally able to get him settled into an activity with one of his teachers another child came up to him and smacked him in the face.  It wasn't a hard smack, but it shocked Bear.  He went from whining to full on sobbing.  The teacher nearest Bear picked him up to comfort him, and the other teacher ran across the room to redirect the hitter.  Unfortunately, she wasn't fast enough, and he hit Bear again.  The teachers both apologized to me, and I didn't say much.  As the situation was under control, I left.  I knew my staying would only prolong how long it took Bear to calm down, and frankly, I wasn't sure I could be in the room with the hitter.

So here is the dilemma.  The hitter has some sort of developmental delay.  I'm inclined to think he is autistic, but I have no confirmation of this.  I know an aid comes in to work with him every day; I know he gets speech therapy; and I know there are pictures and charts posted around the room reminding him of the rules and the schedule.  I also know he takes his clothes off regularly and that, at 3, he doesn't yet speak, nor is he potty trained.  I've seen some behaviors that suggest autism, but I haven't asked.  It also isn't the center's practice to disclose which children have disabilities or what those disabilities are.  I do think, however, that Bear may be learning to hit in certain circumstances from this child.  Considering how hard we've worked to get Bear to stop hitting, I really don't want to start all over. But I'm not sure what to say or even how to broach this with Bear's teachers, both of whom were Wild Man's teachers and both of whom I really like.  I realize there is only so much they can do, given the rules of the center--time out isn't an option, and it likely wouldn't work for this child.  But I think there must be a way to let the other children know not to mimic the hitter's behavior.  Thoughts?