"As a child I was immature," Hader said following Tuesday's All-Star Game, according to the Wall Street Journal's Jared Diamond. "I said some things that are inexcusable. There's no excuse."
"I'm ready for any consequences," he added.
Hader's account was set to private shortly after the tweets circulated during the All-Star Game.
According to Yahoo Sports' Jeff Passan, the news spread quickly to his family members in attendance at Nationals Park in Washington, D.C.:
Hader, who allowed four hits and a three-run home run in 0.1 innings of work, now faces potential discipline from Major League Baseball.
MLB Chief Legal Officer Dan Halem told reporters the league will consider releasing a statement on Wednesday, according to the Los Angeles Times' Bill Shaikin.
"The situation is what it is," Brewers center fielder Lorenzo Cain said, per the Washington Post's Jorge Castillo. "I know Hader. He's a great guy. I know he's a great teammate. I'm fine. Everybody will be OK. We'll move on from it."