Several residents called 911 after hearing loud cries of sorrow in a Chandler neighborhood after a Tempe man shot his baby son and then himself.
Rajneesh Saini, 25, walked out of a family gathering about 2 a.m. Sunday and carried out the shootings in his parked vehicle, according to Chandler police.
The 3-month-old child was found on his father's lap. Police released Saini's name Monday but not the child's.
Chandler police spokesman Seth Tyler said investigators haven't uncovered a motive for the shootings.
"Even though it's very apparent to us that it's a murder-suicide, we still complete a thorough investigation," Tyler told The Arizona Republic. "We rule everything out, and you do that by talking to everyone you can and gathering all the information you can."
Police said the family gathering was held at the home of a relative of the child's mother.
In the 911 audio recordings released by Chandler police Monday, a man in a calm voice tells authorities "it's a suicide and he killed my grandson also" over the sounds of a woman screaming in the background.
"He shot the baby in the head, and he shot himself in the head," the baby's grandfather said. "It just happened. They are in the car."
The Arizona Republic reported that cries could be heard throughout the Chandler neighborhood, and several residents phoned police.
"We are far up the street, and we still hear screaming," said one 911 caller. "Somebody is really yelling."
"I hear screaming like they're in pain," another caller said. "I just heard a lot of screaming."
**Correction [Aug. 26, 2013, 1:40 p.m.]: An earlier version of this story incorrectly identified the age of the child. EastValleyTribune.com regrets the error.