South Carolina Gov. Nikki Haley (R) warned that the divisive rhetoric presumptive GOP nominee Donald Trump is known for can lead to tragic events like the racially-motivated massacre last summer at a Charleston church.

“I know what that rhetoric can do,” Haley said in a Thursday interview with the Associated Press. “I saw it happen.”

Dylann Roof, a 22-year-old Confederate sympathizer, was charged with murdering nine black parishioners last June at a historically black church. Roof published a manifesto online outlining his white supremacist beliefs, and also uploaded dozens of photos of himself posing with guns and the Confederate flag.

In the wake of the killings, Haley started a national movement to remove the Confederate battle flag from government buildings by advocating for it to be taken down from the state house grounds.

She told the AP that she wished Trump would use a more civil tone in his public addresses instead of resorting to disparaging rhetoric against women, Muslims and Latinos.

“The way he communicates that, I wish were different,” Haley said.

The South Carolina governor, who is of Indian descent and endorsed Sen. Marco Rubio (R-FL) in the 2016 race, has spoken out against Trump’s “irresponsible” rhetoric about immigration many times during the campaign.

Trump responded by calling her “very weak on illegal immigration.”

Despite their differences, Haley has said she will support Trump as her party’s nominee.