Caught nanny having sex! UPDATE

Although this happened last night I'm still livid!!!! We recently hired a part time live in/ overnight nanny to watch our 4 yr old and 6 month old. We have hidden cameras all around our home for our children's safety which we never enclosed to the nanny since none were in private area like nanny's room or bathrooms. Me and my husband had a date night and I checked in on the cameras as I always do. Well to my surprise the nanny was getting busy on OUR brand new expensive sofa! With my 6 month old a few feet away in his pack and play! I called her like 100 times in a row and she never answered. My husband calmed me down as we drove 45 mins back home. I wanted to tear her face off for disrespecting my home and kids. Keep in mind she's engaged and the guy on camera was definitely not him. Her fiancé is Hispanic and the guy on camera was obviously white, blonde hair, and tattoos. Once we arrived she was cleaning and her boy toy was gone. I went in and had a FIT. Calling her every dirty name in the book. Told her to get out and that we would mail her crap. I couldn't stand looking at her anymore. My husband was the only thing stopping me from crushing her face. My question is should I let her fiancé know? I've met him a few times and he's a sweet guy who deserves better. She used him as a reference and I still have his number. I let her agency know what happened so hopefully she doesn't get the chance to fuck on the clock anymore. I'm still upset. I have never even had sex with my baby in the room and to have a stranger do it baffles me. Opinions