What can i do to Protect my family!?

My son was threatened by a man ,the man looked for him for hours and when he found him he told him to leave his family alone and that he has no problem killing him and burying him six feet under. He also was standing at the end of his driveway with a shot gun when my fourteen year old went by on his bike calling my son over and my son just raced home and told me. So i called the police had the man charged and from what i`ve been hearing hes not exactly a very nice man ,he was sent to jail ,apparently he was already on probation for something similar.By the way this was all over something happening between my 15 yr old and his 14 yr old.Now i was told today that he called his son`s cell phone when he was on the bus with my daughter asking if any of my kids take the bus with him (the 14 yr old) the boy said yes and hung up the phone.My fear is will he retaliate and hurt my son or any other member of my family. What should i Do!!!??? please someone help!