These three words denote some kind of accident or mishap. This could have happened to Sid or Arthur, or not.
It could just be the Author trying to come up with something for #FlashFriday and hoping that if he wrote, "Boom, crash, shudder," something would come to mind.
"Hah," hahed Sid who was hanging around, "I've come to mind, something in your mind."
"What?" whatted I, "does that make sense?"
"It could mean that I am now minding something in your mind."
"I don't know, what are you thinking about?"
"I am supposed to be thinking about Kendra and the Wolf Master."
"Do you mind?"
"If I help you."
"It's not supposed to be a comedy you know Sid."
"Is anything you write really funny?"
"What!" exclaimed I, insulted by my own creation.
"Too many whats in this short story," and so he was off before I could make him suffer a boom, crash or shudder.