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Three members of a Pomona family were discovered fatally shot in their beds and the man believed to be responsible was found dead nearby in what police were investigating Friday as a possible murder-suicide.

A possible murder-suicide was being investigated May 9, 2014, after four bodies were found in a Pomona home. (Credit: KTLA)

The bodies of a 52-year-old mother, her 17-year-old son, her 25-year-old daughter and the daughter’s 28-year-old boyfriend were found by investigators Thursday night, according to police.

The incident occurred in the 2100 block of Ramsey Way (map).

A male relative contacted police just before 11 p.m. Thursday after the boyfriend called him and said he intended to harm the family, Pomona Police Department Lt. Mike Keltner said.

Within minutes, police got to the home, but no one answered the phone or the front door.

Officers broke in and found four bodies in three different rooms, according to a news release from the Police Department.

All four appeared to have died from gunshot wounds inflicted by a handgun, Keltner said.

“It appears to be domestic related, but we’re not sure why the actual homicides occurred and why he killed himself,” Keltner said.

The mother, son and daughter were each found in their respective beds, Keltner said.

The son and daughter were likely awake and the mother was asleep when they were shot, he added.

The boyfriend was found at the daughter’s feet and a handgun, believed to be the murder weapon, was found nearby, police said.

Keltner initially said the length of their relationship was not clear, but in the news release, police later called the man the daughter’s boyfriend. He may have lived at the home, the release stated.

“Detectives are still trying to determine the reason for the shooting and so far it appears that the suspect may have had a domestic dispute with his girlfriend and for unknown reasons he allegedly shot and killed his girlfriend and the other two family members in the house,” the news release stated.

A surviving daughter, April Mejia, identified the victims to the Los Angeles Times as her mother, Manuela Padilla, 52; sister, Mariana Padilla, 25; and 17-year-old brother, Juan.

There were no previous incidents reported at the home or connected to the suspected shooter, Keltner said.

Keltner said the relative who contacted authorities may have been a brother-in-law related to someone involved, but he could not confirm the information as of Friday. The Times reported that the caller was the alleged shooter’s brother.

The coroner’s office had not identified the victims as of Friday morning.

Neighbors told KTLA that the mother had recently argued with the man over his lack of employment and immigration status.

Witnesses with information related to the homicide investigation were encouraged to contact detectives at 909-620-2085. Anonymous tipsters can call 800-222-8477 or 800-782-7463.’

KTLA’s Melissa Pamer contributed to this article.