Mass shootings in Buffalo, New York, and Uvalde, Texas, this spring captured Americans’ attention and led to calls for gun reform. A proposal that has garnered support from Democratic and Republican lawmakers has been to raise the age to purchase rifles from 18 to 21. One of the leading voices pushing for the change has been Connecticut Democratic Sen. Chris Murphy.

In an effort to make his case, Murphy claimed that most school shooting killers are 18 or 19 years old. Fact-checkers at PolitiFact examined the data about school shooters and ruled the senator’s claim “mostly true.” But the truth is quite different. That’s the topic for this edition of Fact Check Check™.

Sen. Murphy made headlines with a May 24 speech on the Senate floor following the Uvalde school massacre in which he urged his fellow lawmakers to do “something” to address gun violence.

“I’m here on this floor to beg, to literally get down on my hands and knees and beg, my colleagues, find a path forward here,” Murphy said. “By doing something we at least stop sending a quiet message of endorsement to these killers whose brains are breaking, who see the highest levels of government doing nothing.”

During an appearance on CNN later that day, Sen. Murphy explained that one of the “somethings” Congress could do would be to raise the age for rifle purchases from 18 to 21.

“I want to get rid of these assault weapons, but maybe we can find common ground on just limiting who can get access to them,” he said. “Maybe say you have to be 21 instead of 18, seeing that most of these killers tend to be 18, 19 years old.”

It is true that the shooters in both Buffalo and Uvalde were 18 years old. But is that the case with most school killers?

Following the statement from the senator on CNN, PolitiFact decided to fact-check whether “most of these killers tend to be 18, 19 years old” and asked Murphy’s office for details. The office responded by pointing to a Washington Post database that tracks every act of gunfire at elementary and secondary schools since the 1999 Columbine massacre.

The Post’s database that Sen. Murphy’s office cited, which included shootings in which someone did not die, revealed that about 70% of school shooters were under 18. This means that most school shooters, because they are minors, are already banned from buying the type of assault-style weapons used in Uvalde and Buffalo.

The most common ages for school shooters, according to the Post, are 15, 16 and 17. In fact, the paper’s data show that the number of 15-year-old shooters is twice the number of 18-year-olds, three times the number of 19-year-olds, and about eight times the number of 20-year-olds.

PolitiFact’s analysis cited the Post data and pointed out that the vast majority of school shooters are under 18, but then ruled that Sen. Murphy’s claim was “mostly true.” The outlet even gave the lawmaker credit for “slightly understating the case.”

Our ruling: This fact check is flat-out false. PolitiFact’s fact-checkers got it wrong: Most school shooters are not 18 or 19 years old but are minors who are already banned from buying the weapons Sen. Murphy is worried about. PolitiFact knew that the facts cited by the senator directly contradicted his claim, but its team ruled it true anyway.

That’s just the latest evidence that fact-checkers need their own fact checks and why Fact Check Check™ exists.