If you ask mental health researchers, such mass shootings are much more complicated than that.
"This is a mental health problem at the highest level," he said. "It's a very, very sad event."
But those statistics have "almost nothing to do with mass casualty shootings," said Jeffrey Swanson, a professor in psychiatry and behavioral sciences at Duke University who specializes in gun violence and mental illness.
So exactly how are mental health and gun violence intertwined, and what is needed to end the violence?
There's no doubt that America's systems of care for mental health are overburdened, expensive and inaccessible for many who need them, he said. But when it comes to gun violence among this community, suicide tends to occur at higher rates than homicides, he said.
"If we back up and think about firearm-related injuries and mortality as a public health problem, it turns out there is a mental health-related story, and it's suicide," he said. "If we had better mental health care and could get people better access and break down barriers to care, then yes, we might reduce gun violence by a lot but it would be from reducing suicides."
Otherwise, mental illness is just one "highly unspecific" factor that may contribute to gun violence, along with being young, white and male, or a history of violence, Swanson said.
Swanson supports intervention at the point of purchase through comprehensive background checks -- but to make background checks work, criteria for inclusion on the database should be based on other indicators of risk besides mental health history, such as those indicators of aggressive, impulsive or risky behavior.
"A history of violent behavior is a far better predictor of future violence than mental illness," he said.
Calling gun violence a mental health issue is to scapegoat and stigmatize people with mental illness, he said.
"It's kind of a canard, a convenient explanation that exploits the tremendous fear people have with these horrifying mass shootings," he said. "If people fear those with mental illness they're going to treat them with scorn and support public policies that restrict their liberties."
After all, mental illness affects millions of adults across the country.
"Reducing the incidence of gun violence will require interventions through multiple systems, including legal, public health, public safety, community, and health. Increasing the availability of data and funding will help inform and evaluate policies designed to reduce gun violence," according to the association's website.
They conducted household surveys with 9,282 people from February 2001 to April 2003, excluding people who carried guns for work, resulting in a response rate of 70.9%.
An analysis of the survey results estimated that nearly one in 10 adults has access to firearms and has a problem with anger and impulsive aggressive behavior.
These people were more likely to be male, younger and married and to live in outlying areas around metropolitan centers rather than in central cities, Swanson and his colleagues wrote in their paper.
They were significantly more likely to meet diagnostic criteria for a wide range of mental disorders, including depression, bipolar and anxiety disorders, PTSD, intermittent explosive disorder, pathological gambling, eating disorder, alcohol and illicit drug use disorders, and a range of personality disorders.
What's more, despite evidence of "considerable psychopathology" in many of these respondents, only a very small proportion, 8% to 10%, were ever hospitalized for a mental health problem.
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"So how was it that he was able to get a gun? By all the facts that we seem to know, he was not supposed to have access to a gun," Abbott told CNN's Chris Cuomo. "So how did this happen?"
On Monday, Trump said his "thoughts and prayers" were with the victims and their families but did not suggest plans to take any legislative or other policy action to address the shooting.
Correction:Texas authorities previously reported the youngest victim was