Four people — including a young child — were discovered fatally shot in what appeared to be a murder-suicide at a Queens home on Monday, law-enforcement sources said.

The bodies were found inside an apartment in a four-story building at 23-07 30th Drive in Astoria at around 9 p.m., according to the sources.

Two of the victims were women, one was a man and the fourth was a child believed to be about 5 years old, the sources said.

Police were called to the scene after a cleaning woman walked into the apartment and discovered the carnage, a source said.

“Upon entering that location, they observed, in quick time, four individuals that were apparently the victims of gunshot wounds,” NYPD Chief of Detectives Dermot Shea said at an impromptu press conference Monday night.

Before long, other cops swarmed the residence as a police helicopter flew overhead.

Shea added that police were looking into the possibility that the tragedy was a triple murder and suicide.

The man’s throat was apparently slashed in addition to his being shot, a high-ranking police source said, adding that a gun was recovered at the scene.

Shea said cops had a tentative identification on the man but his name was being withheld. The identities of the other three victims were still being determined early Tuesday morning.

One neighbor described the man as jovial.

“He was the happiest person I’ve ever seen,” said the upstairs neighbor, Steven Levine.

“He has parties in the back yard — a tall, happy guy.”

Sources said the man was a physical therapist who recently had been dealing with financial and family problems.

In an online posting, he lamented that a custody battle for his son was “destroying my current marriage and life.”

“I had the perfect life a few years ago but it has spiraled out of control and I desperately need any help you can provide,” the man wrote.

Despite that clue, it was uncertain which victim had shot the others before committing suicide.

Additional reporting by Tina Moore