When Debra Denison went to a day care center to get her grandchildren Tuesday afternoon, nothing seemed out of the ordinary. She had her daughter's permission to pick up 6-month-old Ashton and 2-year-old Alton.

But this time, police said, she had a gun, and she had written a suicide note.

Police aren't saying why Denison, 47, killed her grandsons and herself, but court papers and relatives detail a history of mental instability and suicide attempts in 1989 and 1990.

A 5-inch-thick divorce case on file at Superior Court in New London — filed in 1989 by her second husband, Keith Rowley, and spanning several years — includes documents that say Denison attempted suicide at least three times and was committed to the psychiatric ward at The William W. Backus Hospital in Norwich for more than a month in early 1990. Documents in the file indicate she struggled with alcohol, committed crimes and was found by a judge to be not competent to care for her children.

Investigators have not released Denison's suicide note, but the boys' paternal grandmother said police told the family that she wrote that God spared her 13-year-old son. Denison was supposed to pick up her teenage son, Jason, before she headed to the day care to pick up her grandsons.

Donna Connors, Alton's and Ashton's paternal grandmother, said Wednesday she was not aware of any recent problems concerning Denison. She said she was aware of Denison's health issues, which she said her daughter-in-law described as bipolar disorder and other ailments.

"She'd pretty much been fine lately," Connors said, noting that Denison had been taking medication.

"Something had to have snapped," Connors said, although she said she can't understand why, if Denison wanted to take her life, she had to take those of the children.

Tuesday began normally for the Perry family. Ashton and Alton were dropped at Kidds & Co. day care in North Stonington. The day before, Brenda Perry, 23, made cupcakes for her son Alton's birthday, which was Tuesday, and wrote about it on her Facebook page.

"Can't believe 2 years old already," she wrote. "So blessed."

Police and family said that Denison was on the list of people allowed to pick up the children from day care, as she did on Tuesday at 2:30 p.m. because her daughter had a doctor's appointment.

Denison did not show any sign of distress when she picked up her grandchildren, said Christine Hare, co-owner of the day care center.

"Everything was as normal as we would want it to be," Hare said. "We go over it in our minds."

No one heard from Denison after she picked up the children and her cellphone was off, Connors said. Police said it appears that Denison drove to a boat launch at Lake of Isles and shot the two boys before turning the revolver on herself.

The three were found after an Amber alert sparked a frantic hunt for the children and Denison. A passerby saw the van, recognized it as the one described in the Amber alert and called police about 9:30 p.m. Tuesday.

Denison left home with a weapon Tuesday, state police Lt. J. Paul Vance said. State police Sgt. Donna Tadiello said the handgun was a revolver. She didn't have information about whether it was registered.

On Wednesday, Perry thanked people for their prayers in a Facebook post that noted that her mother was "sick."

"Thank you for the prayers … My boys are in an amazing place we got a few great angels watching over us," she wrote. "Love you Ashton and Alton."

Children's toys sat in the side yard of her family's North Stonington house Wednesday. Brenda and her husband, Jeremy, are devastated, said Connors, who lives next door.

Connors said the boys were "the most happy-go-lucky, interested little things you've ever seen."