Experts: Circumstances of Florida family slayings 'really unusual'

(CNN) -- The early-morning slaughter of four Florida siblings at the hands of what authorities say was their mother is an "almost unheard of" case, crime experts said Wednesday.

Investigators are still trying to determine what happened at the Port St. John home of 33-year-old Tonya Thomas early Tuesday morning. But Patricia Pearson, author of "When She was Bad: How and Why Women Get Away with Murder," said mass killings with women as a perpetrator are rare -- and when they do happen, they typically aren't committed with guns.

"If a gun was used, that's almost unheard of," Pearson told CNN.

Women make up about 5% of the ranks of mass killers, said James Alan Fox, a criminologist at Northeastern University. And most cases in which women kill their families involve young children, said Fox, the author of "Extreme Killing: Understanding Serial and Mass Murder."             Full Read