The "guerrilla blown up in van" was a member of the rebel movement seeking to overthrow the government in Val Verde in 1987. He was killed when Alan "Dutch" Schaefer's private military team attacked the main guerrilla camp in the jungle, and was in fact the first casualty of the assault.
The guerrilla was patrolling the jungle camp when Dutch and his team begun their assault. When Dutch sent a driverless pickup careering into the camp, the guerrilla jumped aboard, attempting to stop it before it ploughed into the main palapa, not knowing there was a satchel charge in the back of the truck. He got into the driver's seat, but was already too late to stop the vehicle crashing into the structure, and the moment it struck the satchel charge detonated, blowing up the guerrilla and several of his comrades who had been inside the building.
The soldier was armed with an AKM assault rifle, although he never had a chance to fire it.