notify the police.
Here's a story about the same thing, it was happening to my sister and she wouldn't let go, my dad hit the roof when he found out that he was hitting her,
My dad is an ex member of the Coffin Cheaters Motorcylce Club, so he called up toothy and Dave and me, my dad toothy and dave payed him a visit i had to wait in the hall way but i saw my dad and toothy walk in with two peices of wood and dave with a hammer then my dad took me outside shut the door, but me being me i put my head agaisnt the door and listened to what was haepping there was alot of swearing a few lound grunts thena loud bang and sream of pain, they opened the door carryed out the tools and they lefty him a message.