Chanel Lewis, 20, was arrested and charged with second-degree murder after the medical examiner's lab matched his DNA to evidence from the crime scene and under Vetrano's fingernails.
He is being held without bail after his arraignment in the Howard Beach slaying. Her body was found on Aug. 2 amid the weeds in a marshy park not far from her Queens home.
Police sources said in May, a man who works in the NYPD Chief of Detectives office saw Lewis around his neighborhood on the Brooklyn/Queens line and thought he was suspicious, sources said. He called it in, but Lewis was gone before patrol officers arrived.
The next day, sources said a 911 call was made about Lewis, because he looked like he was about to break into a property with a crowbar.
Last week, Lewis was considered as someone police should look at in Vetrano's murder, sources said. Police found a summons and tracked Lewis down. Last Thursday, he took a voluntary DNA swab. Last Saturday afternoon, sources said the medical examiner's office reported a match with his DNA at Vetrano's crime scene.
Lewis was arrested three hours later and confessed, sources said. But his father, Richard Lewis, doesn't believe the accusations.
"He is a wonderful young man," he said. "Wonderful. And he is great. He is good. He wouldn't have done whatever I see, whatever I heard. He wouldn't have done it."
Chanel Lewis does not have a prior record. He is due back in court on Feb. 21.
Lewis, who does not work, lives in East New York with his mother. Police have not yet determined a motive, but they do not believe he was stalking or knew Vetrano. Sources said Lewis was "unhinged" and apparently upset because of the number of people in his apartment.
Lewis' arraignment was very emotional for Vetrano's parents, who saw the man accused of killing their daughter for the first time.
Vetrano's devastated parents spoke out before heading to court for the arraignment, thanking everyone for their support and their love for Karina. They also expressed their gratitude to the NYPD and the community.
"The police did an excellent job," dad Phil Vetrano said. "They solved this through good, old, hard police investigative work."
"They worked endlessly and tirelessly, and that was because of their passion, combined with our passion for our daughter," mom Cathie Vetrano said. "We would stop at nothing to find the savage that did this to her."
Phil Vetrano vowed that his work is not yet done, and he will follow the legal process to the very end.
WATCH THE FULL NYPD NEWS CONFERENCE ON THE ARREST: