The lunatic who killed three people in a horrific New Jersey murder-suicide was an estranged father who gunned down his kids’ mother and her parents, authorities revealed Wednesday.

Vaughn Stewart, 37, stormed the Berkeley Township home where his former lover, 38-year-old Deonna Stewart, lived with their three children Tuesday, NJ.com reported, citing investigators.

He allegedly shot Deonna’s parents, Allan Russell, 61, and Michelle Russell, 60, before chasing her down a street in the normally peaceful, leafy neighborhood, police said.

Stewart furiously fired multiple shots that struck and killed Deonna — before walking back to the home and turning the gun on himself, the outlet reported.

The three children were left unharmed.

Stewart, of Maplewood, had been living separately from Deonna, who had moved with their three kids into a home owned by her parents, according to police.

The heinous triple-homicide broke out on Fairwood Avenue at around 5 a.m., terrifying neighbors as gunfire rang out and cops flooded the area, according to the Ocean County Prosecutor’s Office.

Neighbors described the Russells as a church-going couple that was well-liked in the neighborhood.

“They were truly great, great people,” James Casella, 41, told NJ.com Tuesday — adding the slain pair was friendly and even gave his own three kids backpacks once.

“It really hit us hard,” he said of the senseless slaughter.