lets look at 4 columns, if we can't find a winning strategy for that then more columns won't have a winning strategy either.
Label the columns 1,2,3,4
Shoot column 2 three times, if he started at 1 or 2 he's dead.
if he started at 3 he winds up on 4. shloot 4 he's hit
If he started at 4 he winds up at 3, shoot 3 he's hit
since you can't be sure where he is you can't gaurantee to hit him
if the number of shots you take at column 2 is odd, he winds up at the other available position, if even he winds up at the same position. Since you don't know where he started then you can't gaurantee to hit him.
I would be very interested to see a winning strategy for 4 columns