Mike Tyson said that “the devil himself” would show up Friday night in his boxing match against Jake Paul. He gave Paul a preview at Thursday’s weigh-in.

After Tyson weighed in at 233 pounds, he approached Paul for the final stare-down before Friday’s clash at AT&T Stadium. Paul, who weighed a career-high 220 pounds, darted forward from a crawling stance to get up close and personal to the former heavyweight champion.

In response to Paul, 27, entering his personal space, Tyson unleashed an open-handed slap that connected flush on Paul’s face. The two were quickly separated by security as Paul played to the crowd, mocked Tyson and laughed at him.

A source close to Tyson told ESPN that Tyson reacted to Paul “purposefully” stepping on his foot during the stare-down. Tyson was fed up with Paul’s trash talk, according to the source, and stepping on his foot was the tipping point for Tyson.

Tyson was escorted away while Paul addressed the crowd, saying, “It’s personal now. He must die!”

Tyson’s demeanor has shifted over the past several days. He was talkative during Tuesday’s open workouts but appeared much more subdued at Wednesday’s news conference, offering short answers to questions from the media. By Thursday, he seemed to have had enough of the talking and was ready for action.

How that translates to Friday’s bout is anyone’s guess, but the slap has only heightened anticipation for the generational clash between the iconic boxer and the YouTuber-turned-prizefighter.