4 yr old assaulted by classmate

At daycare my 4 year old daughter was laying on her stomach reading when a boy, also 4, came up from behind, pulled down her pants and laid on top of her.  My daughter seems confused about what happened.  She has enjoyed this center for over three years and I am thankful that they were very straightforward in their reporting of this incident.  
The question is: what do I do now?  Should she see a therapist?  

[Sandman2]

   I would think that at age 4 seeing a complete stranger (therapist) would be kind of not good.  If any thing, you should get some kind of professional advice about how you should  deal with this.  If you have experienced daycare people (and sounds like you do as she has been going there for 3 years), I think I would let them handle the situation.  They know what happened and the kids involved.