Levi Parker called his estranged wife on Dec. 23 and told her it would be the last time she ever heard from her children.
The panicked mother, Stacy Flowers Parker, called Pima County sheriff's deputies, who arrived at the house within five minutes and tried to get Parker's attention from outside, Arizona's Daily Star reported.
“Soon after, deputies heard one gun shot and they forced entry into the home. Inside, they found the father and two daughters, all with gunshot wounds," Prima County Sheriff Chris Nanos said.
Parker and his 5-year-old daughter Haylee died a few hours later after they were brought to Banner University Medical Center. Mackenzie Parker, 8, died at the scene.
A male neighbor said he witnessed the drama.
"It completely blindsided us," the unnamed neighbor told KOLD-TV. "Like we were home and it sounded like someone pounding a nail on a board."
Carey Ruziska works near Parker's condo complex, and was nearby when sheriff's deputies pulled up to the residence.
"You cannot imagine a bigger nightmare for a mother," Ruziska said. "You cannot imagine that. How unbelievably sad and devastating that would be."
The daughters were staying with their father because he had visitation rights, the sheriff told local media. Levi and Stacy Parker were in the middle of a bitter divorce and custody battle. Joan Parker, the girls' aunt, told the Daily Star that Levi was upset that his wife began dating another man.
“He did not want another man with his girls,” she said.
Levi, a former National Guardsman who was employed at defense contractor Raytheon, seemed happy when he posted his youngest daughter's Christmas wish list on Facebook just a month earlier, according to KOLD-TV.
"This is tough," Nanos said. "It's a couple hours before what's supposed to be the best day in the world for little kids ... our community lost two little ones."