The Queens dad who massacred his family Saturday blasted his baby mama to death in a fit of jealousy and shot his two daughters because he’d rather see them die than go into foster care after the attack, sources said.

Jonathan Walker, 34, was overheard at a liquor store the night before the attack, telling anyone who would listen that he was convinced his common-law wife, Shantai Hale, was being unfaithful.

“He believed she may have been cheating on him — possibly with more than one person,” a law enforcement source said. “He went and got drunk that night before heading home.”

After pounding drinks, Walker skipped his nightclub security gig Friday evening. Flowing with liquid courage, the murderous man instead showed up around 5:30 a.m. Saturday at his gal pal’s Springfield Gardens home, where he methodically executed 7-year-old daughter Kayla and badly wounded her 12-year-old sister, Christina.

“He wanted to kill the two kids because he didn’t want them in foster care” after he killed their mom, a source said.

Walker then went to another bedroom and fatally shot Hale, 31, and her mother, Viola Warren, before committing suicide in his parked car at JFK Airport.

“He destroyed a whole family,” said Hale’s cousin Joseph Simmons. “There are no words to describe how angry the family is. He is a loser. He is a coward.”

Christina survived the rampage and managed to dial 911 to explain her father’s barbaric deed. She even opened the door for first responders.

Relatives said Christina is in a medically induced coma and undergoing intensive care following surgery that involved cutting open her skull to ease brain swelling.

“The doctors are hopeful,” said the girl’s uncle, Silford Warren. “Thank God the bullet passed through the part of her head that it did. She moved her head backward at just the right moment when [her father] fired and that probably saved her life.”

Additional reporting by Kevin Sheehan