Who drives these vehicles is unknown. In the intro video of Shadow of Chernobyl, the driver appears to be a former Duty stalker. He is wearing a PSZ-9d Duty suit, as evidenced by the four red chest panels in the bulletproof vest and somewhat dark color of the suit. This leads some to suspect that the newly-inducted subjects drive these trucks, explaining why these stalkers have not yet been given the Monolith colors.
All known Death Trucks are ZIL-130s, a civilian-purpose truck.
It is thought that you could find a Death truck at Cordon in Shadow of Chernobyl. It is located a little south of the abandoned military outpost that connects Cordon and the Garbage level. The vehicle is tipped over and surrounded by gravitational anomalies and high levels of radiation. A lot of bodies of Monolith and other factions soldiers are lying around, that could be a giveaway that it's a Death truck. It could be the same truck Strelok was rescued from, since his rescuer went to Sidorovich on foot. But this also brings the question of how the truck got there. as it would have had to gone though the military check point.