The former Gossip Girl star, who wed longtime girlfriend Jaime Feld on Saturday (03Aug13), has revealed he was in Vancouver, Canada when his pal Monteith died in a city hotel following an accidental overdose.
He tells Bello magazine, "There was a group of us who were there... it's been very, very strange."
Zegers reveals he flew back to Los Angeles with some of Monteith's ashes, adding, "He's probably the closest person I've ever lost... Cory was the nicest man I knew."
And the death of his friend has served to remind the actor that there are so many 'normal' people suffering with substance abuse and addiction issues.
He adds, "It's a f**king horrible disease... I think it's something that constantly reveals itself as something that happens to people who, for whatever reason, don't get well, and it was by no lack of him trying or anyone else trying to help him get well. Eventually, your body just says, 'No, it's enough'.
"But it doesn't make it any less sad or tragic. I think the problem people had was that he looked healthy and he never showed the struggles he was having."