A man in Arizona shot his mother and teenage sister before pulling the trigger on himself in an incident that police believe was a murder-suicide case.

The three dead bodies were found after the mother's boyfriend arrived at their Mesa apartment Monday night, according to ABC15 Arizona.

The boyfriend told authorities he was living in the apartment with the trio, identified as Aide D. Popoca, 46, Rafael Popoca, 21, and Ashley Popoca, 14, before the mother and children were found dead with gunshot wounds.

The boyfriend made the gruesome discovery when he went back to the apartment after work on Monday. He immediately called 911.

Officers arrived and found the woman and her children in separate rooms of the apartment. Further investigation led officers to believe that Rafael had shot his mother and sister before ending his own life.

"It is very early in the investigation and details may change as the investigation continues," Mesa police said in a statement released Wednesday morning, as quoted by azcentral.

Other family members were shocked and heartbroken when they heard the news. A close family member told AZ Family that they don't know what triggered the murder-suicide.

"I think it could have happened anywhere and it just happened here. Prayers are with them. Hopefully, they have a strong family support system or church system to help them through it," Phill Scott, a neighbor, told the outlet.

Derek Murphy, a frequent visitor at the apartment complex, said people experiencing homicidal or suicidal thoughts should reach out for help.

"Seek help immediately, don't wait around for it," he told the outlet. "If you need help, go get it. There's a lot of help out here that you can get."

The circumstances that led to the shooting were not clear.

If you have thoughts of suicide, confidential help is available for free at the National Suicide Prevention Lifeline. Call 1-800-273-8255. The line is available 24 hours, every day.

A police line
Representation. A police line. SimaGhaffarzadeh/Pixabay