A drug lord is being transported to the maximum prison cell, where it would be harder for him to escape. If he ever wants to escape, now would be the time to act since if goes to the maximum prison cell, it would be impossible to escape. That is why; the cops assigned a sharpshooter to protect the van. The idea here is to protect the van. Don't any of the enemies gets close to the van. If the van gets destroyed then you failed the game. Each kill would earn you money, You can buy better guns and some men with the money.