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The grieving widow of slain New York City Police Det. Jason Rivera described through tears the terror-filled moments when she learned through cell phone apps and technology that her husband was one of the officers gunned down by a domestic violence suspect

"Today, I'm still in this nightmare that I wish I never had. Full of rage and anger – hurt and sad, torn," Dominique Luzuriaga Rivera told the thousands of mourners who packed the pews of St. Patrick’s Cathedral in New York City. "Although I gained thousands of blue brothers and sisters, I'm the loneliest without you."

REMEMBERING NYPD DET. JASON RIVERA: THOUSANDS FLOCK TO NYC'S ST. PATRICK'S CATHEDRAL TO HONOR HERO COP

She was held by another woman as she spoke for about 10 minutes, struggling through tears and a shaky voice at times to finish her sentences. 

READ THE FULL TEXT OF DOMINIQUE RIVERA'S EULOGY FOR HER HUSBAND

Just one week earlier, she and Rivera, a 22-year-old police officer assigned to the NYPD's 32nd Precinct, had an argument before they left each other. 

"You asked me if you are sure that you don’t want me to take you home. ‘It might be the last ride I give you,’" she recalled him saying, as she grew more emotional. "I said no. And that was probably the biggest mistake I ever made."

Rivera said she hailed an Uber and returned home. Later that day, "I received the call I wish none of you that are sitting here with me will ever receive."

The "nightmare" began with a notification from the Citizen app, a breaking news application that notifies users in real-time when crimes are being reported nearby. It streams the crimes or breaking news and allows users to stream live video from the scene. 

"I saw that two police officers were shot in Harlem. My heart dropped," she recalled. "I immediately texted you and asked you, ‘Are you OK? Please tell me you’re OK. I know that you’re mad right now but just text me you’re OK. At least tell me you’re busy.’"

When she got no response, she checked Rivera’s location using Apple’s Find My iPhone software and saw that he was at Harlem Hospital.

FALLEN NYPD DET. JASON RIVERA'S GRIEVING WIDOW CALLS OUT MANHATTAN DA BRAGG IN HEARTBREAKING EULOGY

She thought he might have been waiting for a crime suspect, she explained. "But still, nothing." 

"I called, and then called again and then called one more time. And this time I felt something wasn't right," she added.

Rivera said she began calling her husband’s fellow officers but got no answer. 

Then, she got a call from someone asking if she was "Jason’s wife … And that I had to rush to the hospital." 

"Walking up those steps, seeing everybody staring at me was the scariest moment I've experienced," Rivera said. "Nobody was telling me anything. Dozens of people were surrounding me. And yet I felt alone.

"I couldn't believe you left me. Seeing you in a hospital bed, wrapped up in sheets, not hearing you when I was talking to you broke me. I asked why. I said to you, ‘Wake up, baby. I'm here.’

"The little bit of hope I had that you would come back to life, just to say goodbye or say, ‘I love you,’ one more time had left. I was lost. I’m still lost."

Mikey Light, a spokesperson for Citizen app, told Fox News Digital Friday the company's "thoughts are with Dominique Luzuriaga and her family as they grieve the tragic loss of" Det. Rivera. 

Thousands of law enforcement officers from across the country and the world joined loved ones and the public on Friday in paying their final respects.

NYPD’s Commissioner Keechant Sewell announced during her eulogy she had promoted Jason Rivera to Detective First Grade posthumously.

Sewell told the crowd New York City has always been "a city of lights."

"And Police Officer Jason Rivera was one of the brightest," she said. 

Rivera and his partner, Officer Wilbert Mora, 27, were shot Jan. 21 while responding to a report of a domestic violence incident in Harlem involving a mother and her adult son, Lashawn McNeil. 

Along with a third officer, the pair met with the woman and had begun to approach the back bedroom, where they were told McNeil was staying. As they approached, McNeil opened fire and struck Rivera and Mora. The third officer returned fire and critically injured McNeil. 

Rivera died Jan. 21 shortly after the shooting.

Mora, who took a gunshot to the head, succumbed to his injuries Tuesday. He donated his organs and was ultimately able to save five lives. Mora's services have been scheduled for Feb. 1 and Feb. 2 and will also be held at St. Patrick’s Cathedral. 

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McNeil allegedly used a high-capacity magazine and a handgun, both of which were found to have been stolen. He died from his injuries Monday.