Witnesses indicated that the suspect arrested in connection with the Sunday attack in Boulder, Colorado, utilized a makeshift flamethrower and tossed an incendiary device, according to the city and the FBI. 

Press releases also noted that the suspect was heard yelling “Free Palestine,” during the attack.

Boulder Police Chief Stephen Redfearn said during a Sunday press conference that “a man was throwing Molotov cocktails and using other devices to hurt people.”

But what are Molotov cocktails? 

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“The term typically refers to a glass bottle filled with flammable fluid and capped with a lit cloth fuse or wick soaked in alcohol. When thrown against a hard surface, the bottle breaks causing the wick to ignite the cocktail’s liquid as well as its vaporized fuel,” West Point Professor Sean Watts explained in a 2022 piece available on lieber.westpoint.edu.

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Earlier this year, some U.S. soldiers learned about making Molotov cocktails from Estonian soldiers, and then hurled them into a wall, creating fiery explosions.

Video footage shows what happens when the devices are used.

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None of the victims of the Colorado attack have passed away, the Boulder Police Department noted in a post on X.