BOSTON (AP/CBS) — U.S. Sen. Elizabeth Warren says there’s a difference between fighting hard for a principle and encouraging people to violence — but she declined to say if President Donald Trump has crossed that line.

The Massachusetts Democrat made the comments Thursday in an interview with The Associated Press as the mail-bomb scare widened.

Warren said the bombs are a reminder that some individuals have stepped over the line. She said they are responsible for their actions, but added that it’s important no one incite anyone to violence.

U.S. Sen. Elizabeth Warren in Worcester (WBZ-TV)

At Clark University Thursday afternoon, Warren said she’s worried for everyone, calling the pipe bombs a threat to democracy.

“I don’t know what the motivation is, because I can’t get myself in the head of someone who would try to engage in that kind of violence,” Sen. Warren said. “What I know is that it’s wrong and the person or people who did this are responsible. I have great faith in our law enforcement both that they will keep us safe and that they will find the people who did this. It may take a while, but they will find them.”

Warren is a frequent target of Trump who has repeatedly mocked her by calling her “Pocahontas,” a reference to Warren’s claims of Native American heritage. Warren has released DNA test results that provide some evidence of a Native American in her lineage.

Warren said she has not received any suspicious packages.

(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)