I know someone who owes support

My friend is in a relationship with a very abusive guy. He owes his ex-wife
over $13,000 in child support. My friend just had a baby by this guy 3 months ago. He doesnt work and is abusive like I said to her. She cant get him to leave. When she trys he threatens her( I will kill you, you will never get rid of me) He abuses her mentally and physically. If I was to turn him in to the child support system how long would he be in jail or would he even go to jail if the ex-wife isnt persuing the support. Also he has a warrant out on him right now for failure to appear in court. He tells her to call the police because he will only be in jail for 60 days and then come and get her.

Please help... so I can help my friend.

Thank you