I'm hearing reports that the guy driving the tug/buggy has got bad spinal injuries.
Having driven many different types, these Beltloaders are certainly not the safest things to drive due to the position of the driver and most can go very fast which can cause them to bounce out of control due to the weight of the belt or rocket launcher and if the driver is not belted down he too will bounce causing him to lose control (I stress this is just a thought).
But my fear is that turnround times has a big part to play in this as they were probably both rushing to get to their aircraft.