Cops are investigating a scary fire attack at the home of UFC star Anthony Pettis -- after someone set the fighter's cars ablaze in the middle of the night and then sped from the scene.
It all went down around 1 AM on Thursday morning at Pettis' home in Milwaukee.
Investigators believe the suspect used an accelerant to ignite two of the vehicles -- and the flames spread to the 3rd car ... which were all located in Pettis' driveway, according to FOX 6.
Unclear why Pettis was targeted. So far, no arrests have been made and no suspects have been named.