Colin Farrell ''freaked out'' when an obsessed fan called at his house on Saturday (16.11.13).
The intruder was arrested after trespassing on the 'Total Recall' star's property while he was at home in Los Angeles.
The unidentified man walked up to Colin's front door, which led to him calling his assistant, who then called police. The trespasser was taken into custody after officers talked to him, and placed under a 5150 involuntary psychiatric hold.
Under Californian law an officer can place a person under this hold if they have ''probable cause to believe that the person is, as a result of mental disorder, a danger to others, or to himself or herself, or gravely disabled.''
The man is not thought to be a US citizen, and is believed to have travelled to Los Angeles specifically to see the Irish star.
Colin has two sons, James, 10, and Henry, three, by different women and he is particularly protective of his eldest son, as he suffers from Angelman Syndrome, a rare neuro-genetic disorder that can impair speech, movement and balance.
He has previously said: ''Things like walking and talking and eating and feeding himself, all those things that so many of us naturally take for granted because they come so easily, to James, they come somewhat harder. Everything he's achieved in his life has come through the presence and the kind of will that is hard work. He's someone to be inspired by.''
It is unclear whether either of Colin's sons were with him at the time he was approached by the intruder.