On the Administration console, right-click on the name of the target cluster in the left panel.
Choose "Kill this cluster ..." from the list of options.
The Administration console will ask you whether that is really what you want to do. Click "Yes." All the affected servers should immediately stop work. Node Manager will kill any server that does not respond.
To confirm the success of the operation, click the Tasks node in the left pane. On the Tasks page, click the shutdown task's name. Then click the Details tab.