Ut oh! Hunky heartthrob and Taylor Swift's ex Jake Gyllenhaal, who is the rumored subject of 'We Are Never Ever Getting Back Together,' made a visit to the ER (Nov. 13) and was hospitalized after punching a mirror. Whoa! WTF?

Ease up! Gyllenhaal, 32, wasn't freaking out or having a meltdown or on a rampage. It was an on-set accident while the actor filmed an intense moment as a crime scene reporter for his film 'Nightcrawler' in Los Angeles.

Thank God it was his hand and not that pretty face that was injured!

A source told PEOPLE that the actor "flipped out" for a scene during which his character was staring into a mirror and punched it in anger. But it seems JG went overboard with the method acting. The actor cut himself "so bad he had to be taken to a hospital."

An insider said, "The scene was emotionally charged and his character was talking into a mirror and he got so into it, he banged his hands against the mirror and it broke and cut him. It was all the scene and not because he was mad about anything else."

He received stitches in the ER and returned to the set later in the day. What a pro!

Again, Gyllenhaal is taking his role seriously and not just because he got a boo-boo on the set. JG even dropped 20 lbs. for the role, with another source saying he has been "starving himself" for the part.

He does look gaunt and drawn in the photo above. He def looks better with meat on his bones, but we applaud his commitment to his art.