Several protesters were removed from Donald Trump’s rally on Thursday after they silently held up pocket-sized copies of the Constitution during his speech.

{mosads}The Republican presidential nominee was talking about the border when he was caught off guard by the demonstration, which appeared to take place several rows back but in line with the stage at the Portland, Maine, rally.

“You know, we have another thing, we have 16,500— you can do whatever you want,” Trump said, interrupting himself. “Go ahead, do whatever you want.”

The crowd chanted “USA” and loudly booed the protesters as they were escorted out, still holding up what appeared to be small copies of the Constitutions.

Maria Testa, one of the protesters and a member of the Maine People’s Alliance, blasted Trump for his “personal cruelty and hateful rhetoric.”

“Right now, we all have a choice,” she said in a statement. “We can either stand up to defend what’s best about America or we can tell our children that, in this critical moment, we did nothing to oppose the racism, bigotry and inhumanity of Donald Trump and his supporters.”

The demonstration invoked Khizr Khan, a Muslim-American man whose son, Humayun Khan, was killed while serving in Iraq as a U.S. Army captain.

“I and the other activists who stood up today, silently and peacefully, and held up copies of the U.S. Constitution, aren’t just standing up for the family of Captain Humayun Khan,” Testa said. “We’re standing up for the principles for which Captain Khan gave his life.”

Khizr Khan drew national attention last week, when he spoke at the Democratic National Convention. During the speech, he pulled a copy of the Constitution from his pocket and asked if Trump had ever read it.

Updated 6:28 p.m.