He hadn't touched the mouse button. The client did it for him.
Possible countermeasures server operators might deploy eaglercraft 1.5.2 hacked client
Eaglercraft 1.5.2 hacked clients remind us that where there's a game, there's someone trying to break it—even if that game is running in a Chromebook's RAM, 4,000 miles from any official Minecraft server. He hadn't touched the mouse button