Craig Ferguson

All of the late-night shows went on as regularly scheduled Monday night, just hours after three were killed and more than 130 were injured by two explosions at the Boston Marathon. But it was far from business as usual.

"Tonight's show is a little bit different. Obviously, the news of today is so horrendous that it would seem insensitive at best to say 'It's a great day for America,' so I won't be starting the show with that tonight," Late Late Show host Craig Ferguson said in his monologue Monday. "Is anyone else sick of this s---? I seem to have to say that too often. People say to me, 'Craig, your job is to make people laugh at the end of the day.' And I think, yes, that's true, but I've never professed to be any d--- good at that."

At least three dead after explosions at Boston Marathon

Ferguson also touched on his personal connection to the city of Boston and the family he has there. "My first stand-up special in America, I shot it in Boston. I like that town. I'm appalled by this thing and when I watch it on these streets that I know, it's horrifying," he said. "If I have all this inside of me, if I have all this rage and anger and distress and upset inside of me, I'm not a good enough comedian to hide all that from you."

Ferguson was just one of many celebrities who took to Twitter, Facebook and other public forums to express their condolences about Monday's tragedy. Ben Affleck, a well-known Boston native who shot two of his own movies in the city, tweeted, "Such a senseless and tragic day. My family and I send our love to our beloved and resilient Boston." Another famous local, actress and writer Mindy Kaling, wrote, "My heart aches for my hometown."

Remember celebrities we lost this year

Comedian and actor Patton Oswalt penned a widely shared Facebook message speaking about hope for humanity. "This is a giant planet and we're lucky to live on it but there are prices and penalties incurred for the daily miracle of existence. One of them is, every once in a while, the wiring of a tiny sliver of the species gets snarled and they're pointed towards darkness," he wrote. "But the vast majority stands against that darkness and, like white blood cells attacking a virus, they dilute and weaken and eventually wash away the evil doers and, more importantly, the damage they wreak. This is beyond religion or creed or nation. We would not be here if humanity were inherently evil. We'd have eaten ourselves alive long ago.

"So when you spot violence, or bigotry, or intolerance or fear or just garden-variety misogyny, hatred or ignorance, just look it in the eye and think, 'The good outnumber you, and we always will," he continued. Nothing can make death and explosions okay. But at least insights like this can make the future seem better."

Watch Ellen DeGeneres' heartfelt message to Boston from her show: