US law enforcement shot and killed one of the two New York prison escapees, Richard Matt (49), on Friday near the Canadian border.
Police said they are still searching for the other convicted murder, David Sweat (35), who is still on the loose.
Following a briefing from US border Patrol and US Marshals Service, Senator Charles Schumer (D-NY) said Richard Matt was killed by an agent from Vermont taking part in the search operation.
New York Governor Andrew Cuomo said they closed in on Matt following a report by a camper who realised a bullet hole through the back of his place.
New York State Police Superintendent Joseph D'Amico said their search led them to a cabin which is apparently used and recently left by Matt.
Shortly after, the police spotted the fugitive who was holding a shotgun.
"They verbally challenged him, told him to put up his hands. And at that time he was shot when he didn't comply," D'Amico said.
Cuomo said they have no information whether the two escapees were travelling together, and the law enforcement officers have not spotted Sweat yet.
About 1,100 law enforcement officers are continuing the search for Sweat in the area.
Earlier on Friday police found items in a nearby cabin that the pair appeared to have left behind in the area.
Matt and Sweat escaped from Clinton Correctional Facility in upstate New York three weeks ago cutting through their adjacent cells’ walls using construction tools and then sneaking through a catwalk and a steam pipe that led them to a manhole outside the prison.
Corrections officer Gene Palmer (57) and training supervisor Joyce Mitchell (51) were charged with aiding the two convicts for their escape by providing tools smuggled in frozen hamburger meat.
Matt was sentenced to 25 years to life for torture, murder and dismemberment of his boss in Tonawanda, New York 18 years ago.
Sweat was convicted of killing a Broome County Sheriff in 2002 and was serving a life sentence.