CHICAGO (CBS)–Pharrell Williams’ lawyer sent the president a cease-and-desist letter on Monday, after using the song “Happy” at a recent Trump rally in Indiana, according The Hollywood Reporter.

The president played Williams’ hit song at his rally in Indiana on Saturday, just hours after a gunman opened fire at Pittsburgh synagogue, killing 11 and wounding at least six others. President Trump also spoke at a  campaign-style rally in Illinois that same night. He said he considered cancelling his appearance at the Illinois rally following the massacre but decided to go ahead as planned.

“On the day of the mass murder of 11 human beings at the hands of a deranged ‘nationalist,’ you played his song ‘Happy’ to a crowd at a political event in Indiana,” writes attorney Howard King in the letter. “There was nothing ‘happy’ about the tragedy inflicted upon our country on Saturday and no permission was granted for your use of this song for this purpose.”

The letter states Williams “has not, and will not” grant permission for the president to use the song.