Douglas Epp pleaded guilty to attempted murder in the July 2012 episode, which left a Spanish tourist with a spinal fracture. Epp was promised a 14-year prison term; his sentencing was set for Oct. 29.
Visiting from Barcelona, Spain, Hugo Alejandre was eating lunch with his girlfriend in a park surrounding New York's City Hall when a business-suit-clad man sitting next to them pulled out a hammer and started clobbering Alejandre with it, the Manhattan district attorney's office said. Bystanders ultimately grabbed the tool.
Epp was arrested nearby, and police said they collected the bloody hammer and a 5-inch-long steak knife from his jacket.
Prosecutors described it as an unprovoked, entirely random burst of brutality toward a total stranger.
Epp, however, told investigators he "lost it" after he believed he overheard Alejandre and his girlfriend making derogatory remarks about him.
"This is not my demeanour, and I am ashamed this altercation occurred," he told investigators when he was arrested, according to court papers.
While the case appeared straightforward at first, authorities soon realized they didn't actually know who allegedly did it.
Epp initially gave them a phoney name — one that really belonged to a former acquaintance, an American who was working in finance in Vancouver and is known in Canadian chess circles.
The chess player, John Yoos, saw news reports and recognized the tall, bald man in the news photos as Epp, whom he'd known casually in Winnipeg and Vancouver but hadn't seen in about a decade.
Yoos called authorities, and prosecutors soon concluded Epp was using an alias. He'd given not only Yoos' name but his birth date.
Epp also agreed Tuesday to plead guilty to a misdemeanour identity theft charge for posing as Yoos.
A judge ordered a psychiatric evaluation of Epp this June, court records show.
Epp has been in New York since about 2010, his lawyer has said. He told investigators he was looking for a job on the day of the attack.
Politely answering a judge's questions, Epp didn't expound Tuesday on the hammer episode or his identity manoeuvr. His lawyer, Alyssa Gamliel, declined to comment.
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