This statement is true. After doing some research, USA Today said that "a male suspect was taken into custody on Sunday after multiple people were set on fire during an event calling for the release of Israeli hostages in Gaza at a pedestrian mall in Boulder, Colorado". A pro-Israeli group was protesting (like they usually do) outside of a mall, for Israeli hostages in Gaza, when a man threw a bottle filled with a flammable liquid and fuse at the end of it -also known as a Molotov Cocktail- into the crowd. There was also a flamethrower involved, apparently. The police say that eight people were injured, according to the BBC. These news sources covered this incident quickly and got the necessary details about the case as soon as possible.