Someone help

Okay so my daughter to my best knowledge has never been sexually molested she is 8 but tonight I caught her in her room naked with her brother naked on top of her.   I'm scared for her and am already going to take her to a crisis counselor   I'm wondering how I should handle this my emotions are going haywire and now I must also take my son to a counselor cause of this incident    Does anyone know of any good advice.   Please don't give me any hurtful comments she spends half the week at her dads I just don't know where this came from cause I restrict what they watch hear etc to be age appropriate.  HELP PLEASE