In what is certainly unexpected news to hit the rock world today (January 9), Three Days Grace lead singer and co-founder Adam Gontier has resigned from the band.

The Canadian rockers announced the sudden departure on their official website this morning. The reason for the singer's decision is apparently over non-life threatening health issues. Gontier informed his former bandmates of the decision last month according to Three Days Grace's official statement below.

We appreciate everyone’s concern about Three Days Grace. We found out on December 21st that Adam wished to resign from the band. In a letter to us Adam indicated that he was resigning from the band due to a non life threatening health issue and wanted the band to continue moving forward without him. We were as shocked as many of you were to hear the news. Three Days Grace has always been and will continue to be not only our job but our passion.

The post continues to state that Three Days Grace will not cancel their co-headlining tour with Shinedown next month. Guitarist Brad Walst's brother Matt, who is the vocalist for My Darkest Days, will fill in for Gontier for the time being.

"We've been hanging out and rehearsing with Matt and look forward to rocking the stage in a few weeks," the statement continued. "As of right now, Matt's role is temporary and as far as the future and beyond this tour, we are taking it one day at a time."

While some may speculate that Gontier's past battles with drug addiction have resurfaced,  he released his own statement to dismiss any rumors of him relapsing.

"The truth is, when I was struggling during that dark time in my life, I hit rock bottom, and I had the kindest of people reach out from all over the world, and reach their hands out to help pick me up," Gontier wrote in a letter posted by Loudwire. "I am so blessed to be walking in the light now. I am reminded of your loyalty, always. The truth is, and I’m very proud to say this…, I am sober. That chapter in my life is over."

Listen to Matt Walst perform vocals on the Three Days Grace single "Chalk Outline" below.

Three Days Grace are set to perform at the Kellogg Arena in Battle Creek along with Shinedown and P.O.D on February 13.

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