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.
Police are investigating whether Gjeli was targeted and whether the ex-boyfriend, who has addresses in both New Jersey and Minnesota, knew the attackers. Gjeli said the men didn't demand money.
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. Officials were waiting to interview the suspect after he was lucid.
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.
Investigators on Thursday said they were searching for Gjeli's ex-boyfriend, who called the building before her shift began and harassed her co-workers. When she arrived at about 3 p.m. Wednesday, she said she also received calls from the man, Aleksander Vacaj. During one call, Vacaj threatened her life and the life of her family, police said.
Vacaj has a lengthy rap sheet in New York and New Jersey for arrests such as witness assault and menacing; Gjeli was also once charged with witness tampering in New Jersey, police said. The two had a seven-year relationship that ended in February, but no restraining orders were issued.
Gjeli filed a complaint against her ex-boyfriend in Carrano's Queens precinct on May 17 after she was slapped in a restaurant. Carrano, 40, was not the investigating officer in the case but was on the squad dealing with complaint.
Gjeli phoned the squad after 6 p.m. to report the harassing calls. Carrano answered, and told her he would stop by after his shift ended. He arrived at the condo around 10:15 p.m.
Both Gjeli, 26, and her family were thankful he was there. The woman's relatives said that the men had "tried to kill her" and that Carrano had "saved her life."
