WATCH: Enraged Trump supporters attack man for quietly sitting with ‘America’s Already Great’ sign

Two protesters sitting quietly at a Donald Trump rally Monday had their signs grabbed out of their hands and ripped up by Trump's supporters before they were booted out by security, according to Boston.com.

Video of the incident shows two bespectacled men sitting at a packed rally in Lowell, Massachusetts. The Washington Post estimates the crowd packed the venue and topped 8,000. The men can be seen holding neon-yellow signs, one read, "America is already great," and the other appears to say, "God bless President Obama," according to Boston.com, though it's not fully in the camera frame.

A man behind them can be seen telling them, "Shut your mouth!"

Another man sitting in front of them turns around and says, "You're at a Trump rally? Ditch those! Ditch 'em!"

The two men then begin grabbing at the protesters' signs, snatching them away and tearing them apart, as other audience members began chanting, "Trump! Trump! Trump!"

The protesters are then surrounded by security and escorted out.

Trump rallies have become regular sites for protesters, who are often violently attacked by supporters or security. In November, an African-American protester was knocked down and beaten by Trump supporters. Last month, another black protester was attacked and  Trump supporter can be heard saying, "Light that motherf*cker on fire!"

Watch the incident, as posted to YouTube by user Harrison Walsh, here: