Marty O’Donnell, the composer for the best-selling Halo video games and the upcoming Destiny, has been fired by the games’ developers, Bungie. He announced the news himself on Twitter, saying that he was given no explanation.

“I'm saddened to say that Bungie's board of directors terminated me without cause on April 11, 2014,” O’Donnell tweeted on Wednesday. That message has already been retweeted 2,000 times, a sign of how popular his work is. Many of his followers replied with stunned tweets, some even left without words.

According to Forbes, Bungie did release an official statement, but offered no further explanation.

“For more than a decade, Marty O’Donnell filled our worlds with unforgettable sounds and soundtracks, and left an indelible mark on our fans,” the company wrote. “Today, as friends, we say goodbye. We know that wherever his journey takes him, he will always have a bright and hopeful future. We wish him luck in all his future endeavors.”

O’Donnell has been crafting the scores for Bungie’s games for over a decade, beginning with his iconic Halo score. His work is beloved by video game fans and Forbes suggested that it his firing is similar to Steven Spielberg suddenly not wanting to work with John Williams any longer.

O’Donnell did not write the score for Halo 4, which Microsoft employed a different studio for.

It’s unknown how this will affect Destiny. According to The BBC, he was working with Paul McCartney on that project, even recording music at Abbey Road Studios in London. Activision plans on releasing that in September.

Here’s a sample of O’Donnell’s work: