Shortly after 7:30 p.m. on April 3, a man found a 46-year-old woman, her 14-year-old daughter and her 21-year-old son all dead in different rooms of an apartment in Mesa, AZ Family reported.
The man is believed to be the boyfriend of the mother, according to the outlet.
Police have not yet released the names of the deceased.
Detectives reportedly believe the 21-year-old man first fatally shot his mother and younger sister before killing himself.
The investigation is ongoing.
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