Vacaj is believed to have orchestrated the attack on ex-girlfriend, Artende Gjeli, who was slashed inside 123 Baxter Street, a luxury condo in Chinatown, on June 28.
Gjeli needed 23 stitches to close wounds on her face, hands and upper thigh after the assault.
A responding off-duty police detective shot the suspects during the attack, killing one.
Vacaj was caught following a massive NYPD manhunt. His attorney had been in contact with detectives with offers to surrender.
The responded officer shot both suspects. The man that was killed was slashing Gjeli, the building receptionist, with a box cutter. The second suspect, who wielded a broken beer bottle, was wounded by gunfire.
But in the process, the officer was slashed in the head.
Police say the detective, Martin Carrano, appeared to be justified.
The receptionist, Artemda Gjeli, had reportedly called Carrano to the Lower Manhattan condominium building on Wednesday night about telephone threats she'd received from an ex-boyfriend, police said.
Carrano and Gjeli were discussing the threats shortly before 10:30 p.m. when two men entered the lobby of the six-story residential building and asked if there were rooms for rent.
When Gjeli, of Lodi, N.J., told the men they weren't in a hotel, they jumped the detective and slashed him, police Commissioner Raymond Kelly said. The attackers then hurtled over the reception desk and began mauling Gjeli.
"She slid to the floor and attempted to fight her assailants as they continued to slash her with sharp objects," Kelly said.
Gjeli was slashed on her hands, knee, thigh and cheek and needed 23 stitches.
The detective, a 20-year veteran, had a 3-inch slash at the base of his neck that required three staples. During the assault, he briefly fended off the attackers and loped through the lobby doors when one of the suspects came toward him, police said.
Carrano fired 10 shots through the doors and hit both suspects twice, then told Gjeli to call 911. It wasn't clear whether he identified himself as an officer before firing.
Eugene Moralez, who was shot in the chest and foot, was pronounced dead at the scene. The second attacker, tentatively identified by police as Andres Camue Martinez, was shot in the arm and abdomen and was in stable condition.
A preliminary investigation showed the shooting appeared to be justified because Carrano faced an imminent threat of serious physical injury or death, said chief police spokesman Paul Browne. The detective has not been involved in other police-involved shootings.
