In the character list, it's states in El Gringo description that
Note that Dynamite damages are not caused by any player.
So my question is: there are other cards which damage is not caused by any player?
Gatling and Indians!
In BANG! FAQ it's stated that Gatling and Indians! are caused by the player who played them.
Q05. Who is considered to be responsible of the elimination of a player with cards like Indians! and Gatling?
A. Unlike the Dynamite, the player who played the Gatling or the Indians! is considered to be responsible of the elimination of a player. All special actions due to this elimination apply to him (for example, if he just killed an Outlaw this way, he draws the 3 cards reward).