FRUIT COVE, Fla. -

St. Johns County Sheriff David Shoar says preliminary findings of a triple homicide investigation finds that a Julington Creek woman killed her two sons and herself inside their home on Thursday.

Donna McCulloch, 40, Daniel Rashley, 8, and William (Ben) Rashley, 7, were found shot to death in the home on Loveland Place -- just off Durbin Creek Boulevard -- about 4:30 p.m. Shoar said it was McCulloch's parents who discovered the body and found the bodies.

While no suicide note was found, Shoar said all evidence points to this being a double-murder and suicide. He said a handgun was used in the killings.

"Needless to say, desperation was, I'm sure, a part of it," Shoar said in a Friday briefing. "The truth is, we're not 100 percent sure what was going through her mind."

McCulloch had been confined to a wheelchair since a June 2010 car crash and also went through a contentious divorce that year.

Shoar said this was difficult case for investigating officers, for the neighborhood and the school where the two boys attended.

School officials said grief counselors were at Julington Creek Elementary School on Friday helping Daniel and Ben's classmates and teachers deal with the news.

"It's not every day that you put math and reading on hold and school grades on hold to talk about life-and-death situations," Principal Michael Story said. "It's not a subject that you want to discuss with 7- and 8-year-olds."

DOCUMENT: Principal Story's letter to parents

A neighbor told Channel 4 that McCulloch had just moved into the home around the Christmas holidays.

"I can't imagine what her parents are going through, and the children's father," Helen Thomas said. "It's too hard."