Weston Cage had gone missing last week in the hours before he went off the hinges and had to be subdued by cops.
The guy who beat him down?
It turns out he had been sent by his dad, Nicolas Cage, to find him.
The one-man search party was 39-year-old Kevin Villegas, who worked as an assistant for Cage for the past five years. Villegas' primary responsibility was looking after Weston, TMZ reports
But last Tuesday, when Weston went M.I.A., sources tell TMZ that Cage dispatched Villegas to track down the 21-year-old and bring him home.
Villegas quickly located his target in L.A., but we're told, Weston was resistant and aggressive -- even threatening to rip of Villegas' "Christian f**king head."
Sources tell TMZ that Villegas immediately reported the situation to Cage,. who instructed Kevin to call 911.
When Weston realized cops were on the way he flipped out and attacked Villegas with the roundhouse kick.
We're told Villegas -- who served with the U.S. military -- feared for his life because Weston is a highly-trained fighter and attacked Cage with a flurry of punches.
Cops came and Weston was hospitalized for a mental evaluation.
Weston says he may press charges.