Last week, a 19-year-old with an AR-15-style assault weapon was accused of walking into a Florida high school and killing 17 people. This week, the nation is embroiled in a debate about who's to blame.

It's the guns. It's the kids. It's gang violence and broken health care and corrupt politicians and violent video games. It's the drugs. It's Russia. It's President Trump.

On Thursday, a Florida middle school teacher weighed in with a Facebook post that has since gone viral, declaring it's the parents.

Kelly Guthrie Raley's post, which was picked up by Fox News, had more than 600,000 shares as of Sunday afternoon. It read: "I grew up with guns. Everyone knows that. But you know what? My parents NEVER supported any bad behaviour from me. I was terrified of doing something bad at school, as I would have not had a life until I corrected the problem and straightened my ass out. My parents invaded my life.

“They knew where I was ALL the time. They made me have a curfew. They made me wake them up when I got home. They made me respect their rules. They had full control of their house, and at any time could and would go through every inch of my bedroom, backpack, pockets, anything! Parents: it’s time to STEP UP!"

Comments read, "Parents have got to do better" and "These horrible acts of violence will continue to happen if their REAL cause is not addressed." The sentiments Raley expressed were pervasive on social media: Tweets and Facebook posts blamed a lack of parental discipline for shootings like the one at Marjory Stoneman Douglas High School.

Ryan Harkness on Twitter wrote: “Guns have always been around and you never heard about school shootings. Now school shootings are becoming the norm. This isn’t a gun issue; it’s a parental and society issue. God taken out of schools, parents failing to discipline their children, and creating entitled kids.”

While John Williams wrote: “Liberals want to blame the school-shootings on gun control. The problem is how our society has allowed people to grow up without consequences, discipline and a sense of ownership. They want to take guns from responsible citizens because their group can't cope with stress/problems.”

But how much are parents to blame? Is lenient parenting part of the problem?

After the 2012 Sandy Hook Elementary School shooting in Newtown, Connecticut., when 20-year-old Adam Lanza fatally shot 20 children and six adults, the National Science Foundation asked researchers to look at what is known and unknown about youth violence. Published in 2016, the report found families do play roles that can either increase or decrease violence. It did not, however, find support for "harsh" parenting, which is viewed as a risk factor.

Researchers said children who had a lower risk of youth violence had "close attachment bonds with consistently supportive caregivers" and experienced "effective and developmentally sensitive parenting."

Raley's argument does not fit neatly in the case of the accused Florida shooter. Nikolas Cruz was adopted. His adoptive mother, Lynda Cruz, died of pneumonia in November and his adoptive father died in 2004. Ethan Trieu, 17 — who was friends on and off with Cruz since the sixth grade — said Cruz changed significantly after the death of his father.

What little we know of Cruz's life does not suggest he lacked discipline or that his family was unaware he was struggling. Neighbours told The New York Times that Lynda Cruz "called sheriff’s deputies to the house numerous times in an effort to keep Mr. Cruz in line.”

Broward County Mayor Beam Furr said during an interview with CNN that Cruz had received treatment at a mental health clinic. The family friends Cruz moved in with after his mother's death took him to a therapist for his depression.

"Mental illness cannot be fixed by parents or caretakers alone either because they are often not financially equipped to do so nor trained to deal with it," said Susanne Babbel, PhD, a trauma therapist. "Children and teenagers with mental illness often need a team of providers but many times do not receive adequate support, nor does the parent or caretaker who tries to meet their child's needs."

When Raley shared her post the morning after the shooting, she might not have been aware of those circumstances of Cruz's life. However, those details were reported by the time many others, including Fox News, picked it up.

One reason her post may have resonated is because she tapped into the frustration other teachers share. Raley notes there were times when she would try to work with families whose children had discipline problems at school and was met with a "horrendous lack of parental support." She isn't alone.

Research suggests one of the major causes of teacher burnout, a long-documented social problem, is the emotional exhaustion they experience while dealing with students' behavioral problems.

In just 45 days, there have been at least six school shootings that have wounded or killed students in the United States. The student survivors of Wednesday's massacre declared “we will be the last." For that to become a reality, people on both sides of the debate — those who share Raley's view and those who do not — will need to at least consider her final thought.

"Those 17 lives mattered," she wrote. "When are we going to take our own responsibility seriously?"

This article first appeared on our sister title USA Today.