Amazingly, the exact instant in which Perez Hilton got punched in the dome during an altercation with the Black Eyed Peas was captured in the photograph below.
The image clearly shows Perez wincing as he was getting socked with a clenched fist, or a nanosecond after the fact. The terrified look on his face tells it all.
It is not clear:

Who the fist belongs to (Perez claims the Peas’ manager, Polo Molina, threw the punch after the blogger and will.i.am got into an argument in Toronto).
Whether that is in fact Lady Gaga on the left.

We’ve seen the video of the Perez-will.i.am fight after the MuchMusic Awards, now here’s the photo taken as heated words escalated into a violent melee:

Guess Perez Hilton wasn’t lying about being punched in the head. Whether the pink-haired’ one’s conduct is to blame for the violent incident is another subject.
The incident ended with the celebrity gossip magnate Tweeting [...]

Source: steve@thehollywoodgossip.com (Free Britney)