ort St. John shooting victims: On the very right is the mother, Tonya Thomas. Top, left to bottom right: Joel Johnson, Jaxs Johnson, Pebbles Johnson, Jazzlyn Johnson.
Port St. John, Florida (FL Today) -- Unfathomable to most parents, Tonya Thomas may have believed she was acting out of love when she allegedly shot and killed her four children early Tuesday morning, say experts who have researched mothers who kill their children.
But it's often a complex mix of motivations and stressors that lead a mother to kill.
"There's no single precipitant," said Phillip Resnick, a professor of psychiatry at Case Western Reserve University in Ohio who started studying "maternal filicide" in the late 1960s. He was a consultant in high-profile cases such as Susan Smith and Andrea Yates, who both drowned their children.
Resnick said Tuesday's shootings in Port St. John appear to be "altruistic filicide" - where a mother believes death is in the child's best interest.
"It's a murder out of love rather than a murder out of hate," he said of how the killer might be thinking about what's happening. "It becomes an extended suicide."
Resnick estimates there are as many as 300 child murders by parents each year nationwide, about half of which are committed by mothers. About 25 percent of the time, the mother will also kill herself.
On average, 10 to 12 Florida children were killed and another three to four were injured annually in murder-suicides or attempted murder-suicides involving parents from 1997 to 2001, said Donna Cohen, a professor at the University of South Florida who has researched the issue.
It's often a "perfect storm" of issues that leads mothers to kill their children, said Cheryl Meyer, a professor of psychology at Wright State University in Ohio, who has co-authored two books about mothers who killed their children.
Often, these mothers at some point struggled with mental health issues and also are struggling with some sort of loss, whether it be a death, divorce or separation.
And they have either lost their social support network - friends and family whom they can rely on for help - or feel as if it is gone, Meyer said.
"They just don't have anywhere to turn. That was (the situation) in every case," she said.
Typically these women are described as "good moms," and see their children as an extension of themselves, Meyer said. So when they decided to kill themselves, they fear who will take care of their children after they are gone or see death as a better option than leaving them without a mother.
"It's not vindictive. It's 'I can't leave this life leaving parts of me behind,' " she said.
What's unusual about the Port St. John case is the age of the Johnson children - all were teenagers or nearing that age.
More often, children killed by their mothers are younger, experts said. Meyer points to mothers finding some respite from the stresses once their children go to school; Resnick said struggling mothers see older children as better able to cope with life without them.
It's also not typical for women to use firearms to kill their children, in part because younger children can be killed by suffocation, drowning or overdose where a weapon is more likely needed to kill an older child, Resnick said.
Yet, many questions about why this happened may go unanswered, Meyer said. Unlike the Smith and Yates cases, there won't be a prolonged trial or psychological analysis.
"We won't be vilifying the mother," she said. "Generally, the public thinks of them as mad or bad. They are either crazy or evil."
Such accusations don't help, even though it may be the easiest way for the public to handle a situation that for some "is too close to home," Meyer said.
"This is scary stuff. It's scary stuff because I don't know very many mothers who don't have conflict," she said.
Susanne Cevenka, Florida Today