What you want to do is very easy in theory, however it risks a crash on the game server so I do not recommend it.
Regardless, here's how you can do it...
Create a target_level_change, and set the mapname value to the name of the map. Set a targetname on this entity as well. When fired, this will effectively reload your map. (This function is bugged and has a chance to crash the game server!)
In multiplayer, all scripts on an NPC are terminated when they die, including the deathscript, which makes no sense. Instead, try setting NPC_target, and give it the targetname of your target_level_change.
Assuming none of these items are bugged, the level should now reload the map when the specified NPC dies.
If you would like a delay before the reload, use a target_delay in between the NPC and the target_level_change.
If you would like printed messages to the players before the level change, use a target_print.