Clues

  1. The man committed suicide. 
  2. The man saw a hitchhiker at the side of the road. 
  3. In the man's truck, there was another hitchhiker. 
  4. The man was a guerrilla. 
  5. The man was carrying guns and ammunition. 
  6. The man was driving in the wrong direction. 
  7. The man realized he was driving in the wrong direction by seeing the other hitchhiker's sign. 
  8. The woman in the man's truck threatened him with a gun. 

Solution

The man was a guerrilla fighter in one of the South American countries. This night, he was driving a truck carrying guns and ammunition for his comrades. He spotted a female hitchhiker and decided to give her a lift. She guided him on a slightly different route, which was supposed to be a shortcut. The man saw someone else on the road and slowed down a bit. It was another hitchhiker, holding a written sign with the name of the city controlled by the government forces. 

The driver realized that the woman in his vehicle was leading him into a trap. He wanted to turn back, but she put a gun to his head and threatened to kill him unless he did what she said. She turned out to be a military agent in disguise. The driver knew all the guns and ammunition inside the truck would be taken over by the government forces, and he would be brutally interrogated. Not to let this happen, he sped up and drove into a tree, killing both himself and the agent.