Just hours after police blasted out an alert that two toddlers might be in danger from their suicidal mother, they discovered their worst fears had been realized: All three were found dead Thursday in a remote, wooded area off Old Gentilly Road in New Orleans East in an apparent murder-suicide.

Michelle McCullum, 25, shot her two children, 3-year-old Cylie and 5-year-old Caden, then turned the .40-caliber handgun on herself, police said. The bodies were found inside a dark blue 2014 Nissan about a mile west of the Interstate 510 exit.

As police cars swarmed the area Thursday morning, weeping relatives arrived to find out what had happened. Mayor Mitch Landrieu and NOPD Superintendent Michael Harrison came in person to deliver the grim news to reporters.

Police said the mother and children were last seen about 10 p.m. Wednesday leaving their home in the 1200 block of Treme Street.

A neighbor, Rick Mathieu, said he overheard McCullum in a brief but loud argument on the street with her husband, Gavin.

“She said, ‘He’s never coming back,’ ” recalled Mathieu, who lives two doors down. “I told her to give it time. I guess she decided she didn’t have time.”

Detectives said McCullum contacted her mother to tell her that she felt suicidal and might harm the children. Police said they issued an alert to officers to be on the lookout for McCullum shortly after that news was relayed to them.

All through the night, said Mathieu, McCullum’s husband paced the streets looking for his wife and children. Around the time when their bodies were discovered, police arrived and picked him up.

“My son is not holding up, because those kids was his life,” said his mother, Crystal McCullum. “That was his life.”

Michelle McCullum had been a second-year student at the University of New Orleans, where she was working on prerequisites for dental hygiene school. Dr. Jacqueline Nesbit, who taught her for two semesters, described McCullum as sweet and a well-liked student who struggled with the classroom material. About two weeks ago, said Nesbit, McCullum told her that the dental hygiene program at LSU had rejected her application.

Nesbit urged McCullum to apply again.

“She didn’t seem that upset to me,” Nesbit said. “She was kind of wondering what she was going to do in the meantime but didn’t seem overly distraught.”

Nesbit recalled McCullum bringing her son to class on several occasions when she couldn’t find someone to take care of him. Like many of those who came in contact with the mother and children, she said they seemed to have a good relationship.

“She seemed happy. Loving. Really kind and sweet to them,” Nesbit said. “I just can’t even believe it.”

Neighbors on the family’s block in Treme also greeted the news with shock. To them, McCullum, who married her husband around the time their son was born, was a doting mother with a ready smile. Her husband adored their children.

“Caden was 5. He was — I mean, just brilliant,” Crystal McCullum said. “Cylie, she was 3, and she was just — she was the spittin’ image of me. … It’s just so hard.”

According to Mathieu, the neighbor, McCullum had acquired the gun that she took her own life with for self-defense; she and her husband used to live in a dangerous apartment complex in New Orleans East where several murders had taken place.

“It’s bad out in the East,” Mathieu said. But in years of knowing McCullum, he said, she never showed any signs of violence.

Mathieu said McCullum worked at NASA’s nearby Michoud Assembly Facility until several months ago when she lost her job; her husband also worked there. She graduated in 2007 from McDonogh 35 High School, where she had been a member of the cheerleading team, said Ryan Billew, a former classmate.

“She was really quiet,” Billew said. “It’s surreal to me.”

McCullum and her children were first discovered by workers from Richard’s Disposal, one of the few businesses on the otherwise barren stretch of Old Gentilly Road. Police were dispatched about 8:15 a.m. The scene inside the car, Harrison said, was so terrible that an NOPD chaplain was called to minister to officers, and he intends to provide counseling for them, as well.

Both children were found on the rear seat floor board of the car with gunshot wounds. McCullum was found in the front seat of the car with a single gunshot wound to the head.

Landrieu briefly addressed reporters near the car.

“These are days that no family, no community and no group of individuals ... ever want to have to respond to,” the mayor said. “Our thoughts and prayers go out, of course, to her family and to the family of the children, for what they’ve lost. It’s another tragic, difficult scene. It just reminds you every day how precious life is.”

Jim Mustian and WWL-TV’s Meg Farris contributed to this report.