Sen. Marco Rubio (R-FL) broke with President Donald Trump on Wednesday night during a CNN town hall discussion on school shootings with the survivors of last week’s massacre in Parkland, Florida, saying that he was not “comfortable” with arming teachers to prevent attacks.

“I don’t support that, and I would admit to you right now, I answer that as much as a father as I do as a senator,” Rubio said, responding to a question about whether he would support a move to train teachers and staff to conceal carry at school. The inquiry came from a Marjory Stoneman Douglas High School teacher who sheltered students in her classroom last week when a former student opened fire on the school, killing 17 people.

“The notion that my kids are going to school with teachers that are armed with a weapon is not something that, quite frankly, I’m comfortable with,” he said.

Rubio said the move would have “practical problems” that would be “about the safety of the teacher as much as anyone else.” He said if a teacher were to pull out a gun in an active shooter situation to protect students, a SWAT team could mistake the teacher for the attacker.

“As a father and someone who has talked to plenty of teachers, including the three in my family and the assistant principal in my family, I don’t think that would be a good idea in my view,” he said.

While Rubio rejected the idea Wednesday evening, Trump indicated on Wednesday afternoon that arming teachers or school staff members “could very well solve your problems.” Trump was speaking to parents and student survivors of school shootings during a listening session at the White House.

“If these cowards knew that the school was well-guarded from the standpoint of having pretty much professionals with great training, I think they wouldn’t go into the school to start off with,” he said. “So we’ll be doing the background checks, we’ll be doing a lot of different things, but we’ll certainly be looking at ideas like that.”

Rubio is not alone in his discomfort with Trump’s idea. The American Federation of Teachers told the Associated Press on Wednesday that arming educators was “one of the worst ideas I have heard in a series of really, really, really bad ideas,” union President Randi Weingarten said.