He also revealed he was looking after Corey's son that night, as their children are friends.
"We got that dreaded door knock," he said, "it was devastating."
Remembering his friend, Garner said: "He wore his heart on his sleeve and he was a damn good coach and he believed in my son and when someone does that... he's a special guy.
"I'm devastated by it. He was my friend. I became friends with him, so I've lost a friend. It's the finality of... I won't see him again. His boy, his family won't see him again."
He finished: "My deepest sympathy and love to the family as well, my deepest thoughts are with you."
