(CNN) Ice hockey coach Bill Peters is apologizing after a former player accused him of using a racial slur against him a decade ago.

Peters coaches the NHL team Calgary Flames in Alberta. The team is investigating him after former player Akim Aliu posted a message on social media saying he directed offensive language toward him.

In a letter addressed to the NHL team's general manager, Brad Treliving, on Wednesday, Peters said he was sorry.

"Although it was an isolated and immediately regrettable incident, I take responsibility for what I said. The statement was made in a moment of frustration and does not reflect my personal values," he wrote.

"I meant no disrespect in what I said, and it was not directed at anyone in particular. But, that doesn't matter; it was hurtful and demeaning. I am truly sorry."

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