Gattis hit a homer earlier in the game and stared down Hernandez. Later, Johnson hit a deep fly ball and was talking crap to Hernandez as he jogged down the baseline, Fernandez's homer was sweet revenge and McCann took offense to him admiring his homer.
IMO, Gattis and Johnson started the drama (mostly Johnson). Hernandez isn't at fault.
Harold Reynolds on MLB Tonight broke the whole thing down beautifully, find the clip if you can, I can't post vids from my phone.
"I give you five minutes when we get there. Anything happens in that five minutes and I'm yours. No matter what. Anything a minute on either side of that and you're on your own. I don't sit in while you're running it down. I don't carry a gun. I drive."