According to a story by David Hinckly at nydailynews.com, the trigger: the arrest of Hot-97's Mister Cee on charges related to a male prostitute.
Flex is a friend of Mister Cee, and apparently he got annoyed when he heard Charlamagne and company talking about Mister Cee's arrest Monday morning.
So Monday night Flex spent about five minutes roasting Charlamagne, though not by name. He also didn't refer directly to Power-105, though his references to "that building" were as clear as the references to Charlamagne.
Flex started by calling the charges against Mister Cee "untrue" and saying, "We don't discriminate against anybody."
But if the unnamed target of his declaration is going to bring the subject up, Flex warned, payback could be coming.
"I know everything that goes on in that building," he said, and dropped a veiled hint that if he made some of that knowledge public, it could be embarrassing.
"You know who I'm talking about," said Flex. "You know the shot I'm sending today. You know the gun I'm loading up today. The choice is yours."