After the crowd at the rally in Phoenix, Arizona, was less robust than expected, President Donald Trump took out his frustration on a former White House aide who organized the event as a contract worker for the Republican National Committee, Bloomberg News reported Monday night.

Once the rally had ended, Trump had an aide inform George Gigicos that he would never do work for the White House again, three unnamed sources told Bloomberg News. Gigicos formerly served as the White House director of scheduling and advance, and he also had worked for the Trump campaign planning rallies. He left the White House earlier in August to return to his consulting firm, and he was helping plan the Phoenix rally last week as a contractor for the RNC.

As Bloomberg News noted, the rally venue was not entirely full when Trump took the stage, an issue for a President obsessed with crowd size and who feeds off the energy of his most loyal supporters. And as Trump droned on through his speech, rallygoers began to filter out and appeared to be uninterested, according to the Washington Post.

The apparent disinterest in his rally—a comfort zone for the President whose White House is roiled by constant internal scandals—clearly bothered Trump. Following the event, Trump claimed that 15,000 people attended the rally, even though a local official estimated that just 10,000 came to the event. He mentioned the rally size again during a press conference Monday, claiming that a “massive crowd” turned out to watch him speak in Arizona.