Tenant has convicted felon boyfriend

[Jazzous Anderson]

Hello everyone, I'm seeking advice, my tenant has a boyfriend who recently was released from jail. He is not on the lease and has spent several days and nights visiting the premises. The tenant lives in my ADU that is attached my main property. The walls are thin and my oldest son can hear them arguing every day. The conversation are really gruesome and often disturbing with statements about killing her many more violent comments. I know I can ask her to put him on the lease but I really don't want him to be no where near the home. What actions or solutions do I have to fix this?