Gunmen killed at least 12 people, and injured more, during today's attack on the Paris offices of satirical magazine Charlie Hebdo. Tonight, Louis C.K. made a powerful statement of support for the French weekly during a show in New York City.

Taking the stage at Madison Square Garden on Wednesday (January 7), the stand-up comic swapped his signature black T-shirt for a red one, on which he had written the words "CHARLIE HEBDO" in black ink.

Since the attack -- which was likely motivated by Charlie Hebdo's satirical cartoons depicting the Prophet Muhammed and ISIS leaders in the past -- has brought issues of freedom of expression to the forefront, it makes sense that the comedian, a man whose livelihood depends on the protection of freedom of expression, would make such a show of solidarity.

The "Louie" star isn't the only person showing his support in the wake of the attack. Journalists and citizens in France, and elsewhere, have gathered to mourn today's victims, united by the slogan: Je suis Charlie.