Chief of staff John Kelly had been pushing Trump for months to fire Pruitt, and he ramped up his campaign in recent days, according to one person close to the White House. The person described removing Pruitt as one of Kelly’s top priorities before leaving the administration, as he’s expected to do sometime this summer.

But Kelly’s frustration with Pruitt alone would never be enough to secure the EPA administrator’s ouster. Trump himself had begun to grow tired of the torrent of negative news stories about him and had come to believe they were a distraction that wouldn’t go away, according to an administration official.

At the White House, senior aides were increasingly convinced that Trump would soon push Pruitt out, but they didn’t know exactly when and some were caught off guard by Thursday’s announcement.