Suspected killer Guy Rivera, 36, was indicted on first-degree murder, attempted murder, and criminal possession of a weapon charges in the fatal shooting of 31-year-old Diller.
Rivera pleaded not guilty to charges of first and second-degree murder. He faces up to life in prison without the possibility of parole if convicted.
Diller's partner took the stand, and jurors saw body camera video of the moments that led up to the shooting.
"What we saw in that courtroom was incredibly emotional for all police officers, for that family. There wasn't too many dry eyes in that courtroom," PBA President Pat Hendry said.
Sergeant Sasha Rosen, who worked with Diller on March 25, 2024, testified that he, Diller, and a third officer were actually done for the day and going to grab food before the shooting happened.
He told the court, "Diller asked for the little lunch bag I had in the back, I passed it to him."
Rosen said it was just out of habit to stop an assist when they drove up on two other NYPD officers on Mot Avenue in Far Rockaway, who were questioning another man.
That's when he spotted Rivera walking with a bulge in the Kangaroo pocket of his hoodie, telling the court on direct examination, " I signaled to Officer Fernandez and Diller, 'Did you see that?'"
Surveillance video that was played in court showed the three officers walking away from the initial police interaction and approaching the Kia Soul where Rivera was in the front passenger seat.
Seperately, Diller is heard on body-worn camera knocking on the window and speaking to Rivera. "Yo, roll the window down for me. Roll the window down. Roll the window down. All the way!"
Rivera only rolled it halfway down and snapped back, "What's the problem?"
"Yo, step out the car. Step out the car. Step out the car. I'm trying to have a conversation with you and you got me talking through a crack," Diller said.
Diller is seen opening the door when Fernandez screams to Rivera, "Yo, don't put your hands in your pocket!"
Right after, a gunshot is heard.
A scuffle is seen and then Diller says, "I'm shot! I'm shot! I'm shot!"
Fernandez screams, "Bro, where you hit?"
Diller responds, "In the leg!"
Rosen, clearly shaken, testified, "As soon as I see the gun, the shot goes off."
On cross-examination, Rivera's attorney challenged Rosen, asking, "Isn't it true that you never told Officer Diller that the person had a gun in the kangaroo pocket?"
Rosen said, "That's false."
"Isn't it true that before any shot was ever fired, that you pulled a gun out of what you thought was in Mr. Rivera's hand?" the defense asked.
"No, that's false," Rosen said.
Defense attorneys for Rivera are trying to prove to the jury that he did not have any intent to shoot an NYPD officer and that the gun went off by accident during the scuffle.
Rivera has 21 prior arrests and has served time for assault, robbery, and possession of a controlled substance.
The cross-examination continues on Thursday.
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