Bullying and the preschooler

I dropped Bub off at preschool today and his teacher told me something that made me deeply unhappy.  He is being picked on by some of the other kids and yesterday someone was pinching him while the others stood around.  It sounds really ominous but they are four.  According to her, Bub was crying and "terrified."  Now I don't know about that because he didn't mention it.  But it would explain why he has been more reluctant to go to school and stopped talking about his friends so much.  He made a point of saying last night that JP was his friend and JA was his friend, even though JA is only in aftercare and goes to preschool somewhere else.  So I don't know what to do.  His teacher is a bit prone to over-dramatics so it might not be as dire as she made it sound.  And I can't protect him all of the time and can only teach him how to stand up for himself in a (hopefully nonviolent) way.  But it worries me that this is going on.  And it infuriates me that she didn't tell my husband yesterday when BT picked him up from school.  We could have done something, had a talk with him when it was fresh.  Instead she waits for me to get him.  Preschools and Dads.  So far, both the daycares he has attended have a hard time telling BT information we need to know.  They wait for me.  DON'T wait for the mom, tell the DAD.  It is ok.  He is a parent too.

But beyond that, bullying at the age of 4 is worrisome.  Four year olds are not known for the good impulse control and empathy.  I don't want Bub to be *that* kid, the one who is picked on.  I don't want him to be the bully.  I don't want this to happen or have happened.  And I cannot stand the idea of him standing around being hurt.  His teacher said she sent notes home to the offenders and, having meet most of the parents, I'm sure they will talk to their kids.  But it's just depressing that we are going to deal with this so soon.