Jack Osbourne got into an argument with his estranged wife, then allegedly got into a fight with her new boyfriend.
Jack went to the home he shares with his ex, Lisa Osbourne, late Monday night to talk to her. Law enforcement sources say things escalated when Lisa's BF, actor/model Michael Gabel, showed up and tried to intervene and thats when Jack allegedly hit the BF in the head.
No charges will be filed, though ... because the victim doesn't want to press charges and Jack has been uncooperative with police.
A source close to the situation said Jack was under the impression he and Lisa were on track to fixing their relationship ... and the BF showing up sent him for a loop. Osbourne's been busy with his show "Ozzy and Jack's World Detour!" with his dad, but remained committed to repairing his situation with Lisa.
Lisa filed for divorce from Jack in May, just months after the couple had their third child.