pointed at by a gun or pointed by a gun

1)You are pointed at by a gun.

2)You are pointed by a gun.

Which one is right when we say a gun is pointed at someone?

#2 is wrong.

#1 is OK, but not very natural. It's not common to express this in a passive way. Saying "a gun is pointed at you" is better.

Or "Someone is pointing a gun at you."
Even in the passive, I prefer the 'ing' form - A gun is being pointed at you.