NEW YORK (CBSNewYork) –  Police arrested a suspect Wednesday evening in the stabbing of two children, one fatally, inside an elevator in Brooklyn.

Shortly after 8 p.m., police arrested Daniel St. Hubert, 27, near 145th Street and 133rd Avenue, just north of John F. Kennedy International Airport in Queens.

He was accused in an attack on Sunday inside the Boulevard Houses public housing development in East New York and left 6-year-old Prince Joshua “P.J.” Avitto dead and his friend, 7-year-old Mikayla Capers, fighting for her life.

Sources told CBS 2 St. Hubert had a kitchen knife with him when he was arrested.

“He had basically kind of a blank expression on his face, you know, he was just — and he hands behind him. He was just walking slowly as they walked him to the car,” said witness Michael Dowery.

Sources told CBS 2 police tracked St. Hubert’s cellphone and zeroed in on his location, walking down a residential street in Ozone Park, Queens.

Police Commissioner Bill Bratton issued a tweet following the arrest.

U.S. Rep. Hakeem Jeffries (D-N.Y.), who represents the area, also issued a statement praising police.

“I commend the police department for its work leading to this arrest,” he said in the statement. “Prince Joshua and Tanaya are in heaven. Let’s hope the police have apprehended a killer who is on his way to hell.

“The hard-working people of East New York have been on edge since the brutal knife attacks that took place over the weekend. The arrest provides a measure of comfort, but this chapter will not be closed until this cold-blooded killer is tried, convicted and put away for life,” he continued.

As CBS 2’s Jessica Schneider reported, cheers erupted in East New York, Brooklyn after police arrested St. Hubert, who had been on the run for three days.

“We said we wasn’t going to rest until we got him,” said P.J.’s mother, Aricka McClinton. “We got him!”

P.J.’s mother emerged from her building to a jubilant crowd. They were all relieved the man who allegedly stabbed two young children, killing Avitto and critically injuring Mikayla, was finally off the street.

Police said in the three days since the stabbing, St. Hubert shaved his head and stayed on the run. He was on parole and missed a scheduled meeting with an officer on Tuesday.

St. Hubert had just been released from prison on May 23, after serving five years for the domestic assault and attempted murder of his ex-girlfriend.

He has nine prior convictions, including assaulting a police officer and assaulting a correction officer.

He was identified by linking DNA off the knife used in the stabbings with the name of someone whose DNA was in the NYPD’s system, sources told CBS 2.

“It’s a shame these people get out for nothing,” said Mikayla’s aunt. “If you assault somebody you should be in there until you’re rehabilitated or something; until they know you’re fixed. For him to kill two people and injure a 7 year old?”

The arrest happened less than an hour after Bratton, Mayor Bill de Blasio and other officials identified St. Hubert and implored New Yorkers to help in finding him. Police were wrapping up the news conference when the suspect was found, CBS 2′s Dave Carlin reported.

Watch: NYPD Press Conference On Fatal Brooklyn Stabbing

NYPD Chief of Detectives Robert Boyce was joined at the news conference on the suspect by police Commissioner Bill Bratton, Brooklyn Borough President Eric Adams, and Mayor Bill de Blasio – who implored New Yorkers to be on the lookout for St. Hubert.

 “The human dynamic here is so deeply moving, so disturbing – two young children on a summer evening on the way to get ice cream,” de Blasio said. “I spoke to the father of P.J. Avitto yesterday. I spoke to his mother today. These parents are in such pain now. As a parent myself, my heart goes out to them, and all of the family members.”

The children had been playing outside under adult supervision when they went upstairs to get some ice cream from P.J.’s sixth-floor apartment.

That was when police said the suspect followed them into the elevator and used a steak knife to stab each child multiple times.

P.J. died at a hospital. Mikayla remains in critical but stable condition. Her family says she is in the Intensive Care Unit with a breathing tube and is in and out of consciousness, but responding to commands.

Police believe the same man may also be responsible for killing 18-year-old Tanaya Copeland, who was stabbed to death just blocks away Friday night.

Boyce said St. Hubert had not been officially named as a suspect in the Copeland stabbing, but his possible involvement remained under investigation Wednesday evening.

Investigators found an 8-inch kitchen knife with a black handle near the scene on Sunday, similar to one used in the attack Friday night.

Meanwhile, CBS 2 has learned that $500,000 was earmarked for surveillance cameras at the Boulevard Houses and other New York City Housing Authority buildings last July, but they only got the go-ahead to install the cameras on Monday, a day after the children were attacked.

NYCHA told CBS 2 the process is complex, but necessarily comprehensive.

Mayor de Blasio said not enough was done and called it “unacceptable bureaucracy.”

“They were sitting on the money for a variety of reasons and I think it was a bad strategic decision by NYCHA,” the mayor said. “By cutting a number of red tape steps in the process, they can get these in place this year.”