Paulo Costa couldn’t allow Israel Adesanya to go unchecked for his questionable remark during Friday’s UFC 248 press conference.

Ahead of Adesanya’s scheduled middleweight title defense against Yoel Romero on March 7 in Las Vegas, the champion participated in a satellite Q&A session with his counterpart in front of fans and media. Much of it was typical pre-fight talk, but one answer in particular raised eyebrows.

Adesanya (18-0 MMA, 7-0 UFC), a Nigerian-born New Zealander, said he would make Romero “crumble like the Twin Towers,” a reference to the September 11, 2001 terrorist attacks on the World Trade Center in New York, which killed nearly 3,000 people. There were sprinkles of criticism from within the MMA community after the statement, but no response was harsher than what came from Costa (13-0 MMA, 5-0 UFC), who went after Adesanya on Twitter.

“You are a disgusting piece of sh*t. How dare you make a joke disrespecting the thousands who died and the heroic firefighters and police,” Costa tweeted. “I will really kill you, dirty kiwi (sic).”

The disdain between Costa and Adesanya has been building for more than a year. Both men have taken some very personal shots at each other, and now it appears the situation has become that much more tense.

It seems like just a matter of time until they share the octagon, too. Costa originally was pegged as the next contender to Adesanya’s title, but a shoulder surgery disrupted the time frame, and Romero ultimately ended up getting the title shot at UFC 248.