The sister of NYPD cop Robert Echeverria, who killed himself at his Queens home Wednesday, said she warned the department that her brother was unstable and might shoot himself if they didn’t try to stop him.

Eileen Echeverria — who lives in West Islip, Long Island — warned the NYPD’s Internal Affairs Bureau in a June 11 email that her brother should not have a firearm, the sister told The Post on Thursday.

“I really am concerned about guns in the house,” Eileen wrote the IAB, according to the email provided to The Post.

She claimed the department did intervene, but just temporarily.

Echeverria’s firearms were taken away — and returned a few days later when an NYPD shrink determined he was not a risk to himself or others.

When an IAB lieutenant let Eileen know that Robert was getting his guns returned to him, she told the lieutenant her brother would use one on himself.

“I said to them, ‘My brother is going to kill himself and the blood is on you,'” Eileen said in a phone interview Thursday night.

“Almost two months to the day, my brother killed himself, and now I have to bury him.”

The grieving sister unleashed on the city and the NYPD for failing to prevent the tragedy.

“The NYPD destroyed my entire family. [They] didn’t give a sh–,” she added.

“When they’re on TV saying they care about mental health, they don’t give a sh–. It’s disgraceful what they’ve done. They killed my brother.”

Eileen said her brother had long suffered from mental health problems and she had warned the department about him at least once previously.

She said he’d had a tumultuous relationship with his wife and had been driven into financial ruin, despite his six-figure salary from the NYPD.

Eileen also blasted Mayor Bill de Blasio for his inaction after the recent spate of cop suicides, calling him “a piece-of-sh– mayor who doesn’t care about police. ”

The NYPD did not immediately comment on the sister’s allegations.