Nurse, 37, and boyfriend found dead in New York City apartment after father heard 'it's over for her' on phone and called police

A father was forced to listen as his 37-year-old daughter was gunned down by her federal agent boyfriend in their New York City apartment in the moments before the killer took his own life.The father then called police, who responded to a Bronx apartment just after 9pm on Tuesday and found Andrea Cantarini, a nurse at St Barnabas Hospital, dead from a gunshot wound to her head.Her boyfriend, Juan Cornelio Diaz, 38, a Customs and Border Protection (CBP) agent based out of John F Kennedy International Airport, was also found nearby, lying dead from a gunshot wound to the head, New York City police have said.Officers are now investigating the incident as a murder-suicide that stemmed from a domestic dispute, as Cantarini's father explained how she wanted to break up with Diaz and, 'He couldn't handle it. He was a coward.''I was on the phone with her for 14 minutes while he was holding a gun to her head,' Rudy Cantarini recounted to the New York Daily News. 'I was begging for her life. And he ended up taking her life.'Police said Cantarini had called her father and told him Diaz was trying to kill her, at which point, he called 911 on another line and told the dispatcher what was happening.He then overheard his daughter screaming and what sounded like three gunshots, according to AMNY. 'I was just begging him to let her go. He just wouldn't do it,' Cantarini said, describing how Diaz told the worried father: 'It's over for her.' Andrea Cantarini, 37, and her boyfriend, Juan Cornelio Diaz, 38, a Customs and Border Protection agent, were found dead of gunshot wounds to the head on Tuesday night. Source: Instagram Police rushed to the scene of their Bronx apartment (pictured) and pronounced them both dead'And then I heard a gunshot. And then I heard the phone fall, and that's it in a nutshell.' The grieving father went on to describe his daughter as 'the apple of our eye.' 'She was a beautiful person inside and out and she was loved by everybody that knew her,' he said.The couple were parents to a six-year-old daughter, and Diaz had a son from a prior relationship, the New York Post reports.Police said they had never been called about domestic incidents involving the couple prior to their untimely deaths on Tuesday.But the couple's downstairs neighbor, Kaela, said she and her roommate heard the couple having a loud argument earlier in the week.'Me and my roommate were having a conversation about like, at what point do we call the cops?' she told the Daily News. 'And then as soon as we had that conversation, they stopped.'Then on Tuesday, Cantarini's grieving father said Diaz 'was acting a little irrational,' prompting the mother-of-one to bring their daughter to her parents' home. Cantarini, a nurse at St Barnabas Hospital, was going to break up with Diaz, her grieving father has said The couple were parents to a six-year-old girl, and Diaz had a son from a prior relationship. Source: InstagramWhen she then went to get clothes from the apartment she shared with Diaz, 'he was waiting for her in ambush.'Soon, Kaela said she and her roommate heard gunshots.At first, she said they thought the sound was simply trucks backfiring. But then they also heard 'the thuds of the bodies, which we didn't know at the time it was that.' 'It's awful and upsetting and horrific,' she said of her neighbors' deaths.'It's a scary world.' Neighbors in their former building also said Diaz and the victim seemed like a happy and successful family.'I always saw them together,' said Karla Evangelista, 29, who bonded with the victim over their both being young mothers.'She was very fit, gym girl, always with gym clothes... She was just amazing and so beautiful,' Evangelista described the victim. 'I still don't understand what led to this,' she said. 'I honestly was so shocked that I didn't sleep, because it was not the people I would have thought that would do that, and that that would happen to her. Authorities are now investigating the couple's deaths as a murder-suicide. Source: Instagram'They seemed like they had a nice relationship and they were so happy to move, to have now a bigger space for their daughter... He was saying to my boyfriend: "We're so happy because now she's going to have her own room,' Evangelista continued.She described Diaz as athletic, talkative and friendly.'He was a good-looking guy, always wearing nice clothes, always biking or running,' she said. 'He was outside with his daughter sometimes, playing right here in the parking lot. [He] would talk to us for like the longest, maybe an hour, standing there, just talking, catching up.'I'm telling you, I never thought this.'Evangelista said she was relieved that their daughter was not present for the heinous murder-suicide.'It's so sad because they took away her life, basically,' she lamented. 'She's alive, but this is going to be very sad.'Other neighbors also expressed their concerns for the couple's daughter, with one 71-year-old describing the six-year-old as 'a sweet little girl.''She was a happy little girl and she seemed to love both of her parents a great deal,' the unidentified neighbor told the Daily News. 'They seemed to be very affectionate towards her.'I would've never imagined this.'The investigation into the fatal shooting is ongoing, but police said they have retrieved the firearm believed to have been used in the murder-suicide.A spokesperson for CBP noted that the agency is cooperating with the investigation. If you or someone you know needs help, please call or text the confidential 24/7 Suicide & Crisis Lifeline in the US on 988. There is also an online chat available at 988lifeline.org.