President Trump will make a "major statement" Sunday at 9 a.m. ET, a White House spokesman said Saturday. The White House did not give any further details.

Mr. Trump tweeted earlier in the night "something very big has just happened!" but he did not elaborate further. He has not tweeted since. 

Though no additional information was given by the White House, Abu Bakr al-Baghdadi, who has led ISIS since 2014, is believed to have been killed in Syria, a source told CBS News.