Story highlights The two singers became friends on tour about a decade ago

Bennington had written to Cornell: "Your talent was pure and unrivaled"

(CNN) After his friend Chris Cornell died two months ago, Linkin Park singer Chester Bennington wrote a letter thanking him for inspiring him and hoping he would find peace in "the next life."

"Your talent was pure and unrivaled," Bennington wrote. "Your voice was joy and pain, anger and forgiveness, love and heartache all wrapped into one. I suppose that's what we all are."

Bennington died Thursday , on Cornell's birthday. Authorities are treating Bennington's death as an apparent suicide.

In his letter in May, Bennington expressed his appreciation to the former Soundgarden and Audioslave frontman for including him in personal moments "with you and your beautiful family."

On Thursday, Cornell's widow, Vicky Cornell, tweeted: "Just when I thought my heart couldn't break any more.....I love you."

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