A Japanese composer working on the Tokyo Olympics opening ceremony resigned Monday after it came to light he bullied classmates during his childhood, the Associated Press reported.

What are the details?

Keigo Oyamada — also known as "Cornelius" — in the 1990s boasted to Japanese magazines and in interviews that, among other things, he forced a mentally disabled boy to eat his own feces and masturbate in front of other students, NBC News reported.

"These reflections were not looked back on regretfully, but instead were seen as funny childhood moments," the popular blog ARAMA! JAPAN wrote, according to the network. "He spoke of them in a boastful nature."

As the start of the Tokyo Games approached, Oyamada's past behavior surfaced online and sparked a backlash on social media that included demands for his resignation, the AP said.

Now 52, the composer said on his Twitter and Facebook pages that "I sincerely accept the opinions and advice I have received, express my gratitude, and will keep them in mind for my future actions and thoughts. I apologize from the bottom of my heart," the outlet added.

Oyamada also said he was "very immature" when he tormented his classmates and felt "deep regret" about what he did, NBC News said, adding that he said he'll "try to be a better person."

The network said Oyamada's critics ripped him, including one Twitter user who wrote, "How can a person who committed such discriminatory and violent acts [be] considered qualified for getting involved in Olympic and Paralympic Games?"

What did Olympics officials, others have to say?

Olympics officials had said Sunday that Oyamada would stay on because he had shown remorse, the AP reported. But hours after Oyamada submitted his resignation, the powers that be reversed their stance and called the composer's actions "absolutely unacceptable" and acknowledged that their earlier decision to let him stay on in light of his apology was "wrong."

"We offer our deepest apologies for the offense and confusion caused to so many during this time," organizers said, according to the AP.

Atsuko Kubo, head of an association of families of the mentally disabled, in a Sunday statement "strongly protested" Oyamada's past actions and said his targeting of the disabled — and boasting about it years later — was disturbing, especially since those with special needs are less likely to fight back, the AP added.

Chief Cabinet Secretary Katsunobu Kato on Monday said Oyamada's past bullying goes against government policy of achieving an inclusive society and "cannot be tolerated," the outlet reported.

Organizers also said Monday that a segment of music Oyamada composed for Friday's opening ceremony will not be used, the AP reported, citing NHK public television and other Japanese media. Oyamada also will be removed from his planned role in the Paralympics opening ceremony, the outlet said, citing NHK.