I was collecting ideas about killcams.
And my final idea was:

Server records all data of every player (position,rotation,shoot,duck, and so on).
After a kill the server sends the last 5 seconds before the kill to the dead client.
Client plays it.
Thats it!

How would you do it?

The client recievs the commands anyway, doesn't it? After all it needs to know how to animate the other players. So why not record on the client? Saves bandwidth on the server.

You may want to look for the Crysis 2 Multiplayer Demo.
It has such killcams where you can even see the bullet.
Basically I would do it the way lemming suggests:
Record the match on the client but make sure you
also simultaneously delete all the data older than
the 5 seconds - it may be too much to handle. Depends on the
amount of used data in the game I guess.

Gamestudio has a built in record/play function (since 6.50), maybe you can use this one.

EDIT: Of course on the client side.

Woah you just need to attach the cam to the players
There is nothing hard. And why u should ise the record function from gs?
On the client all players move so why not just attach the cam?

Yeah, client side would be better, you´re right!
But the build in record function only records my input, doesn´t it?

@chaoscoder
Because i need their movement, like 5 seconds ago and not how they move after my death.
I think you thought of Battlefield, but i mean the killcam like in crysis 2.

A kill cam shows how you got killed from the perspective of the killer (see COD for example). So you have to record the last 5sec for example and play them again