Joo Jin Mo sheds tears on 'Golden Fishery'

Recently, it's been reported that all around tough guy Joo Jin Mo shed some tears while filming for Golden Fishery. He recently had tweeted that, "Hoo~~ filming for Knee Guide~ Came outside~ it's also raining~ feelings are weird as well~ ? thinking if i was showed too much of my real self~ speaking of the past~ also makes me think of drinking~ ke so currently i am drinking by myself~ ? there's no one to drink with me~ ??". He had also tweeted that since he is a man that he shouldn't cry during filming, but failed to do so, and still felt sad even after the filming was over. This has got netizens wondering what exactly happened during filming and hope that he's alright. We'll probably be able to find out in the next coming weeks when it airs! What could have made this tough guy shed tears?