The "Lord of the Rings" star was in a foul mood after spotting a photographer shooting him surfing in Hawaii.
The photog, who one source claims was his neighbor, was snapping pics of Dominic Monaghan on his long board just off the shore before the "Lost" actor stepped out of the water to confront him.
Monaghan was overheard yelling, "What the f*** are you doing?! Why are you taking pictures of me?," exchanging harsh words with the photog before storming off.
The paparazzo apparently didn't learn his lesson though -- he was snapping more shots of Monaghan as he drove away.