You could use an Event Dispatcher.
Every player pawn (or controller or whatever) would bind a custom event to the Event Dispatcher.
The block calls the Dispatcher when someone touches it. The “Someone hit the block” event would thus fire on all players.
Then you set up the inputs of the Event Dispatcher, which would allow the block to send information, such as the name of the guy who just touched the block.
Event Dispatchers are the simplest way of getting a blanket message to a bunch of listeners. They specifically help you when you have no clear idea of who will receive the message - it’s the listeners that have to take care of that, not the sender.
This is roughly what it would look like in the player pawns:
Once the “Bind Event to DeathMessage” node has been used, the pawn will listen for the “DeathMessage” Dispatcher to be called, which then causes “Someone just died” to fire.
This is roughly how the block (or whatever is most convenient) would call the Dispatcher:
Yes, it really is this simple, unless I’m missing something about multiplayer that would make this harder.
This goes into more detail, if you need it: