A Minneapolis mother posted one final family photo showing her beaming alongside her two tragic sons — just hours before her ex-husband gunned them down in a shocking triple murder-suicide, police said.

Kjersten Ellingson Schladetzky, 39, appeared to have been shot inside her south Minneapolis home early Sunday before the youngsters, ages 8 and 11, were killed on the front lawn as they fled – a commotion initially mistaken by a neighbor as something totally benign, the Star Tribune reported.

The mom, whose divorce from her ex-husband David Schladetzky was finalized in June, updated her Facebook with the photo late Saturday, showing her smiling and seated alongside an older woman. Kjersten’s two sons also grin in the snap.

Neighbor Erik Wiltscheck recalled the moment he saw the boys running from the home.

“I thought it was a game,” Wiltscheck told the Star Tribune. “All of a sudden, the gunshots started ringing out.”

The young boys were screaming and ran out of the front door with their coats and backpacks just before being shot, Wiltscheck recalled.

Police officers later found them lying on the front lawn and placed them in squad cars — not knowing whether they were alive or dead.

“This is something that will live with them forever,” police spokesman John Elder said of the officers.

Wiltscheck called the boys “just dynamite kids” who were “full of life.”

The children regularly threw balls over a tall fence into his yard – and were always quick to greet him, he said.

“If I had the chance, I would have traded my life for those kids,” he said. “I just can’t make sense of this.”

Wiltscheck said he also regularly checked in on Kjersten, whose driveway he helped shovel just hours before her David fatally shot her.

The boys were later pronounced dead inside the police cruisers, while Kjersten’s body was recovered from inside her home after a five-hour standoff between cops and David, who died of an apparent self-inflicted gunshot wound, a police spokesman told the Star Tribune.

Kjersten had most recently worked as the director of implementations for Tessitura Network. She also worked as a consultant at the American Museum of Natural History from 2013 through 2015.

“We are deeply saddened and shocked by this news and extend our condolences to Kjersten’s family and colleagues,” said museum spokesman Roberto Lebron.

The case is being investigated as a domestic-related homicide, police spokesman John Elder said.

Police Chief Medaria Arradondo told reporters during a news conference that the “very sad and tragic” shooting left investigators with more questions than answers.

“This is certainly not a conclusion that I as a chief would have wanted,” Arradondo said.