Just woke up to some ridiculousness

So my step children are both at my husband and I house this weekend. It is very rare that we get them on the same weekend. The boy is 7 and the girl is 4...We never have any problems when they come over well last night we put them in their rooms and tucked them in... I went to the restroom about 11 and checked on them and then went to bed myself with my husband. I slept through the night. So when I woke up not to long ago i asked him for the phone charger and he threw it at me with no facial expression or anything I asked him if he was ok if something was bothering him and he just burst out in tears and told me. That he got up around one and his four year old daughter was in his 7 year old sons room on top of him.  He was really upset and said that he was disappointed and did not know what to do. I was furious listening to him and seeing him fall apart the way he was...he said that he talked with both of them and explained that that is NOT ok. He had them separated eating breakfast when I woke up but I don't even know what to do or say to them or my husband in this situation. I asked him why didn't he wake me when it happened and he said that he was embarrassed. What is the next step? What do we do? I have been saying that both of these kids are in very terrible living situations way before this has happened but now they are bringing it into our home and I don't like it! I just would like to hear something positive at this time or some kind of advice on how to handle something like this. My head has been pounding since I found out! I just feel sick like what could have even initiated something like this 😢😢 these are just kids!!!!!