The First Time My Sister Feels Unsafe in Her Home

My sister has been married for several years but this is the first time she generally felt unsafe in her own home. Her husband was finishing up school and they had just had a baby so she was pretty sleep deprived. She wakes up at around 2am to pump in that disgusting feeling creeps up again. The voice definitely does not belong to my brother-in-law. He just starts giggling. It's been a few years and nothing really ever came of it because he technically didn't do anything besides trespassing. They have no idea he didn't injure himself when he jumped out the window.