You have to roll for the crew and the vehicle random selection, and apply results accordingly. Unless you decide to pick one of them per the A14.2 exception:
[EXC: prior to Random Selection, the Sniper may choose one of the following (if present in that Location) as its target: the enemy Sniper counter; a Vulnerable Inherent Crew; or an unarmored vehicle; if any eligible target is concealed, see 14.23].
14.33 vs UNARMORED VEHICLE: An unarmored vehicle and its PRC cannot be attacked by the same Sniper dr. A Sniper attack vs an unarmored vehicle itself can only immobilize it, and only if the Sniper dr were a "1". There is no further effect vs an already-immobilized unarmored vehicle if it is immobilized again. See also
14.22.
14.22 NON-TARGETS: All units are eligible Sniper targets except AFV with no Vulnerable PRC, units in subterranean
[EXC: Caves; G11.8] or Interior-Building Locations, prisoners, or hidden/friendly/Aerial units. Enemy PRC are Vulnerable to Sniper attack if they are CE and/or occupy a Partially Armored AFV or unarmored vehicle. An unarmored vehicle with no PRC (
14.33) can be considered an ineligible target at the Option of the Sniper player.
