The shootings happened just after 8 p.m. Wednesday at 613 Southern Blvd. in the Longwood section.
Police say they found three victims, a 34-year-old man with a gunshot wound to the head and torso, a 57-year-old woman with a gunshot wound to the head, and a 57-year-old man with gunshot wounds to the body.
The 57-year-old man and 57-year-old woman were discovered inside their second-floor apartment and pronounced dead at the scene.
The 34-year-old man was found outside with a gun near his body. He was taken to Lincoln Hospital and was later pronounced dead.
The 34-year-old is believed to have fatally shot his mother, his stepfather and then turned the gun on himself.
Investigators are also looking into whether the 34-year-old turned on the gas and left the bodies inside the apartment in an attempt to cover up the killings.
The FDNY was called for a gas leak after the bodies were found. Firefighters turned off the gas and secured the scene before Con Edison workers arrived.
"Con Edison gas emergency crews arrived to the location at 8:49 last night after receiving a call from the FDNY with concerns about a possible gas issue. We arrived and found that the FDNY had turned off the head of service valve to the three-family home as a safety measure," said Con Edison in a statement.
Neighbors told Eyewitness News a family of three lived in the home for 15 years.
The investigation remains ongoing.
If you are struggling with thoughts of suicide or worried about a friend or loved one, call or text the Suicide & Crisis Lifeline at 988 for free, confidential emotional support 24 hours a day, seven days a week.
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