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Escaped prisoner David Sweat has been on the run for nearly three weeks, 1,100 law enforcement officers are looking for him and his partner in the stunning jailbreak has been killed.

Sweat is more dangerous now than he had been during the entirety of the 21-day manhunt, said Eugene O'Donnell, a criminal justice and law professor at John Jay College and former New York City police officer.

Richard Matt, the other inmate that escaped from Clinton Correctional Facility with Sweat on June 6, was shot and killed by a U.S. Customs and Border Protection tactical team Friday in Malone, New York. Police have pledged to continue a massive manhunt to find Sweat.

"He is face to face with the reality that his life is over, which makes him very dangerous to anyone he comes in contact with," O'Donnell said.

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"He’s obviously in a desperate situation," O'Donnell added. "If he was to be returned to prison, his conditions will be even more intolerable."

Matt, 49, was shot dead by a tactical team in a wooded area of Malone, about 20 miles from the Canadian border, at around 3:45 p.m. Friday, state police said.

If the pair were still traveling together up until the time Matt was killed by police, Sweat may find life on the run alone more daunting, O'Donnell said. "The only thing they really had was they shared a common absurd plan," he said. "Presumably, they were each other's support system."

Matt was armed with a 20-gauge shotgun police believe was stolen from a hunting cabin, and police are acting on the assumption that Sweat may be armed as well.

Police have no evidence the pair split up, and believe Sweat is in the same area. Officers have established perimeter around the area and are searching with police dogs, police said.

These are truly armed & dangerous people & we'll do what we have to do to bring them to justice. If you see something suspicious, dial 911. — Andrew Cuomo (@NYGovCuomo) June 27, 2015

"Sweat is still out there, he's considered dangerous. We're going to continue to look for him and search just as hard until we find him," New York State Police Superintendent Joseph A. D'Amico told reporters Friday. He urged the public to report suspicious activity to 911 or a police tip line.

While nervous residents are waiting anxiously for the drawn-out search to come to an end, O'Donnell said there shouldn't be a rush to capture Sweat.

"The very best time to get this guy would be the crack of dawn where he’s completely exhausted and the dawn of light is broken," O'Donnell said.

But of course, Sweat's movements cannot be controlled, O'Donnell said. "You can never say for sure how these things might end."