Jon Stewart, Conan O'Brien, Jimmy Kimmel and Bill Maher address Charlie Hebdo shootings

Jon Stewart and Conan O'Brien were among several American comedians to weigh in on Wednesday's massacre at the offices of satirical newspaper Charlie Hebdo in Paris, where 12 people were killed, including the editor and lead cartoonist.

“I know very few people go into comedy as an act of courage, mainly because it shouldn’t have to be that," Stewart said on "The Daily Show" Wednesday. "It shouldn’t be an act of courage, it should be taken as established law. But those guys at Hebdo had it, and they were killed for their cartoons.”

The killings, Stewart said, are “a stark reminder that for the most part the legislators and journalists and institutions that we jab and ridicule are not in any way the enemy. For however frustrating or outraged the back and forth can become, it’s still back and forth, a conversation amongst those on let’s call it ‘Team Civilization.’ And this type of violence only clarifies that reality.”

“Of course, our goal tonight is not to make sense of this, because there is no sense to be made of this,” Stewart added. “Our goal as it is always is to keep going, ‘Keep calm and carry on’ or whatever version of that saying is in your dorm room. We spent the majority of our day honestly in shock and grief but also searching for a segue."

On "Conan," O'Brien addressed the tragedy at the top of the show.

“Twelve people were killed because a satirical newspaper made jokes that some group found offensive,” he said. "This story really hits home for anyone who, day in and day out, mocks political, social and religious figures. In this country, we just take it for granted that it's our right to poke fun at the untouchable or the sacred. But today's tragedy in Paris reminds us very viscerally that it's a right some people are inexplicably forced to die for."

"For anyone tonight that has to think twice before making a joke," O'Brien added, "it's not the way it's supposed to be."

On "Jimmy Kimmel Live," Kimmel and guest Bill Maher discussed the killings.

"This happens way too frequently," Maher said. "It's like 'Groundhog Day,' except if the groundhog kept getting his head cut off."

Maher praised Charlie Hebdo staff members for their courage.

"This was a satirical newspaper in Paris," he said. "These guys have the balls of the Eiffel Tower. Their balls were bigger than Gérard Depardieu, because they kept doing it."

Maher added: "We have to stop saying when something like this that happened in Paris today, we have to stop saying, well, we should not insult a great religion. First of all, there are no great religions. They're all stupid and dangerous. And we should insult them, and we should be able to insult whatever we want. That is what free speech is like."

Neither Jimmy Fallon nor David Letterman addressed the shootings in their opening segments Wednesday night.

But other American comedians did. During his show at Madison Square Garden in New York, standup comedian Louis C.K. wore a T-shirt with the words "Charlie Hebdo" written on it.

Speaking at the Television Critics Association winter press tour in Pasadena, Calif., Wednesday, Tina Fey called on the global comedy community to defend the right to satirize.

"You look at [the Paris attack] and you look at the controversy surrounding "The Interview," it makes you think about how important free speech is and how it absolutely must be defended," Fey said. "[We] cannot back down on free speech in any way. We all have to stand firm on the issue of free speech."