A former Irish priest pushed Brazil's Vanderlei de Lima off the road when he was leading the Olympic marathon on Sunday, almost certainly costing him victory in the last event of the 16-day Games.
"The man says he is Irish, he is also drunk. He had been to a taverna earlier," a police source told Reuters.
On Sunday Horan was wearing a kilt and beret and on a white shirt he had pinned the words "The Grand Prix Priest. Israel Fulfillment of Prophecy Says The Bible. The Second Coming is Near." He had a Star of David attached to his kilt.
After being pushed into the crowd, a grimacing De Lima got away from the spectator and rejoined the race, holding his leg, with around 15 minutes to run.
He soon lost the lead to Italian Stefano Baldini. Baldini won the race and De Lima took bronze.
"If that spectator didn't jump in front of me in the middle of the race, who knows what would have happened? Maybe I would have won. It disturbed me a lot," De Lima told reporters.
Police officials said Horan had arrived early on Sunday on a British Airways flight.
He told police that he grabbed De Lima to prepare for the second coming of Christ. "He seems to be suffering from psychological problems," a police official told Reuters.
Horan, born in 1947, ran on to the main Hangar Straight in that race as cars approached at speeds in excess of 240kph. He was sentenced to two months imprisonment for aggravated trespass.
At the Munich Olympics in 1972 a hoaxster snuck on to the track a couple of minutes before the leading runner reached the stadium and ran a full lap, pretending to be a competitor, before being dragged away by security guards.
Four years ago, a well-known Australian prankster broke through security at the Sydney Marathon. He failed to disrupt the race and was soon carted off by police.