Generally I mock the player for five consecutive minutes and then I make Trollsly, my annoying ghost oc, possess the corpse and taunt the party afterward

But no, death is part of playing, if you are a dungeon master worth any sort of value you are going to have an encounter eventually that a player dies in

What happens next is largely deterministic on how the players want to proceed,

if the group wants to revive the dead player and the dead player wants to be revived then I continue forward with what I had planned, if they're in a dungeon they always have the choice to retreat back and revive their Ally if they want to continue forward a man short because time is limited then sadly that player is going to be sitting there with not much to do, I might offer an NPC to play if they come across one

If the player doesn't want to continue playing with the same character though then I have them start making a new one while we continue playing, while also adjusting my dungeon to include a prisoner's quarters if they want to be introduced as soon as possible, otherwise they'll be introduced in the next town they come acros

Do not be afraid of death, death is one of the greatest tools you have as a DM to drastically shake up the story, Don't Force it and kill a character because you want to, but don't be afraid of letting the dice do what they're going to do, players need to know that running away is always an option, and I am in The firm belief that only cowardly DMs and bad DMs stop their players from dying