Tony Mendez, long an on-air fixture handling the cue cards for David Letterman on The Late Showtook the wrong cue this week, assaulting staff writer Bill Scheft, a 15-time Emmy nominee, and getting himself fired, the New York Post reported.

Mendez, 69, who had been with Letterman for 21 years, got into a verbal altercation with Scheft and Letterman over changes in cue cards, went home overnight and stewed about perceived slights from Scheft over a long period. When Mendez came back the next day, he grabbed Scheft by his shirt and pushed him against a wall, the Post reported.

Mendez was kicked out of the theater, and notified Monday that he had been officially terminated from the show, which  Stephen Colbert will take over  next year when Letterman retires. Mendez was also told the show would pay his salary and benefits through Letterman’s departure.

A representative for Letterman’s Worldwide Pants, which produces The Late Show, said the company cannot comment on a confidential personnel matter.

Cameras frequently cut to Mendez during the show’s broadcasts as he handled Letterman’s cue cards. Mendez previously handled cue cards for Saturday Night Live and The Hollywood Palace.