Yup he chose it specifically to be a PITA by all accounts.
Apparently the measures in place are that the firing squad will not see the prisoner when they fire but have been trained to aim at a certain spot, and one of the guns will be loaded with a wax bullet (with the same recoil characteristics as a normal bullet) so no individual will know whether they fired the fatal shot.
Also, the firing squad is no longer available since around 1980something IIRC but because he was convicted prior to that, he was still allowed to choose it.