“We have to be much tougher and much stronger than we’ve been,” Trump said at the fifth Republican debate hosted by CNN in Las Vegas. The answer came in response to a question from Josh Jacob, a student at Georgia Tech, who asked, “How would intentionally killing innocent civilians set us apart from ISIS?”

“You look at the attack in California the other day — numerous people, including the mother that knew what was going on,” Trump responded. “They saw a pipe bomb sitting all over the floor. They saw ammunition all over the place. They knew exactly what was going on.”

“I would be very, very firm with families,” he added. “Frankly, that will make people think, because they may not care much about their lives, but they do care, believe it or not, about their families’ lives.”

Retired neurosurgeon Ben Carson also seemed to agree with a wartime strategy that could result in civilian deaths. Asked if he could issue orders that would kill innocent children and civilians, he made a comparison to his experience taking out children’s brain tumors: “They don’t like me very much [when I say I have to perform surgery], but later on they love me.” Asked if he was OK with the deaths of civilians, Carson said, “you got it.”

The purposeful murder of civilians during wartime is widely considered a crime against humanity. Specifically, under the U.S.-signed Hague Conventions, the U.S. has agreed not to intentionally use violence against civilian non-combatants during wartime. The Fourth Geneva Convention also requires that civilians be protected during wartime.