I have been fishing on several occasions where a Great Egret (large, all white heron) was working the shallows when a Great Blue Heron flew in and harassed the egret out of the pond.
I think the GBH are very greedy for "their" fish. I suspect he was bullying your Green Heron.
P.S. Sorry to hear about Wally, I know he was one of your good buddies! Do you think it was hot water stress and then a cold rain shock that got him?
