(AP) - One of two convicted killers who staged a brazen escape from an upstate maximum-security prison and had been hunted for three weeks was shot and killed Friday, but the other is still on the run.



An official with knowledge of the manhunt said Richard Matt was killed by police and David Sweat is still on the run. The official wasn't authorized to talk about the development publicly and spoke to The Associated Press on the condition of anonymity.



Matt and Sweat used power tools to saw through a steel cell wall and several steel steam pipes, bashed a hole through a 2-foot-thick brick wall, squirmed through pipes and escaped early June 6 from Clinton Correctional Facility in Dannemora, near the Canadian border.



Sweat was serving a sentence of life without parole in the killing of a sheriff's deputy in Broome County in 2002. Matt was serving 25 years to life for the killing and dismembering of his former boss.



A civilian worker at the prison has been charged with helping the killers flee by giving them hacksaw blades, chisels and other tools.



Prosecutors said Joyce Mitchell, a prison tailoring shop instructor who got close to the men while working with them, had agreed to be their getaway driver but backed out because she felt guilty for participating. Mitchell pleaded not guilty June 15 to charges including felony promoting prison contraband.



Authorities said the men had filled their beds in their adjacent cells with clothes to make it appear they were sleeping when guards made overnight rounds. On a cut steam pipe, the prisoners left a taunting note containing a crude caricature of an Asian face and the words "Have a nice day."



Clinton County District Attorney Andrew Wylie said they apparently used tools stored by prison contractors, taking care to return them to their toolboxes after each night's work.



Authorities also said Mitchell had discussed killing her husband, Lyle Mitchell, as part of the plot.



"Joyce Mitchell tells us that was discussed between her and Matt and that upon their escape they were going to return back to Joyce Mitchell's home at which time Matt and Sweat were going to kill her husband," Wylie said.



Lyle Mitchell's lawyer, Peter Dumas, said June 18 that his client was shocked by word of the plot and that Joyce Mitchell had told her husband she couldn't go through with it and the inmates threatened to harm him.



"Toward the end, Joyce had told Lyle - and we have no reason to doubt it - that she told Sweat and Matt that she wasn't going to go through with it," he said. "At that point, they threatened her by threatening Lyle, saying they were going to have someone on the outside do something to him or someone on the inside when he was back at work do something to him, so I think it was a point of control."



Lyle Mitchell was cooperating with authorities and wasn't facing charges.



On June 24, authorities charged Clinton correction officer Gene Palmer with promoting prison contraband, tampering with physical evidence and official misconduct. Officials said he gave the two prisoners the frozen hamburger meat Joyce Mitchell had used to hide the tools she smuggled to Sweat and Matt. Palmer's attorney said he had no knowledge that the meat contained hacksaw blades, a bit and a screwdriver.



Dannemora, built in 1845, occupies just over 1 square mile within the northern reaches of the Adirondack Forest Preserve and is surrounded by forest and farmland. The stark white perimeter wall of the prison, topped with guard towers, borders a main street in the village's business district.



The escape was the first in history from Clinton Correctional's maximum-security portion. In July 2003, two convicted murderers used tools from a carpentry shop at Elmira Correctional Facility to dig a hole in the roof of their cell and a rope of bedsheets to go over the wall. They were captured within three days, and a subsequent state investigation cited lax inmate supervision, poor tool control and incomplete cell searches.