If you take time to read one or two of the Eugene local newspaper or TV stations accounts you'll see the police have no suspects. It could well be related to the shooting but it might not be. No evidence has turned up that ANTIFA was involved. Solid investigators don't "leap" to conclusions, they follow leads, and right now they don't have any.
Luther is probably right about Russian websites and bots. It appears they are spreading unfounded outrage to fuel racial tensions that appeal to America's Right Wingers.