LOS ANGELES, CA - NOVEMBER 25: A protester puts on a gas mask when a large group of protesters are blocked in on all sides by police on an over ramp after protesters ran on to, and blockaded, the 101 freeway following the grand jury decision not to indict a white police officer who had shot dead an unarmed black teenager in Ferguson, Missouri on the night of November 25, 2014 in Los Angeles, California. Police officer Darren Wilson shot 18-year-old Michael Brown on August 9, sparking large ongoing protests. (Photo by David McNew/Getty Images)
An unidentified man was wearing a full gas mask on an American Airlines flight from Dallas to Houston. After passengers became panicked they removed the man from the flight and rebooked him.