"We don’t need crazy conspiracy theories to explain why the police are abusing power," said Sen. Ed Markey (D-MA), who said Americans should 'believe your eyes, not the President.'
In a statement, the attorney for Gugino expressed shock at the President's accusation, which was based on a report aired by the conservative One America Network.
"No one from law enforcement has even suggested anything," said lawyer Kelly Zarcone. "(W)e are at a loss to understand why the President of the United States would make such dark, dangerous, and untrue accusations against him."
Gugino is known in western New York for his advocacy for more liberal causes, like trying to close the Guantanamo Bay prison, working with the group Witness Against Torture.
"Trump callously lied this morning on Twitter about Witness Against Torture’s friend and fellow activist, Martin Gugino," the group said in a written statement.
"Trump should go back to hiding in the bunker instead of tweeting baseless conspiracies about peaceful protestors and further dividing America," said Senate Democratic Leader Charles Schumer.
It wasn't just the President embracing the conspiracy theories about Gugino.
Republican National Committee spokesperson Elizabeth Harrington used a tweet to post an article that claimed Gugino was using a special device filled with fake blood.