We've learned Gerard Butler is under criminal investigation for allegedly assaulting a photog.
It allegedly went down early Tuesday in L.A. Gerard was leaving Crown Bar at 2:00 AM and got into his limo. The photog claims he was following Gerard's limo in a car, when the limo suddenly stopped. Gerard supposedly got out of the limo, approached the photog and asked why he was tailing him.
To that, the photog says he responded, "Hey, that's my job." Gerard allegedly then reached in the car, grabbed the photog's throat and and punched him three or four times. Butler allegedly then kicked the car and again punched the photog three or four times -- close-fisted -- for good measure.
The photog went to the hospital for stitches and then filed a police report. The LAPD confirms they're looking into the case and plan on interviewing Gerard.
No immediate comment from Gerard's people.