This is the second job mission and for it you need to speak to Larissa. Note that you have to have levelled up to Level 2 to unlock this mission. Head to her house in Gamboa, or start the mission from the map screen. The story behind this one is that a man named Orlan from the Disciples gang has evidence relating to the car bomb that killed Ana. Obviously we want to investigate this, so follow the waypoints to find Orlan.
Once he sees you he will run to his car and drive away. Follow him and drive in front of his car. You should then be able to get out and hijack it. The main thing, however, is to make sure Orlan doesn't tell anyone else about what you've done, so you need to kill him. Get out of the car and finish him off. You can then get back in Orlan's car and return to Larissa to complete the mission.
Reward: 750R$
It turns out that the information in Orlan's car was that the bomb was set off remotely, and was not attached to the car's ignition. This means that someone must have been watching you and Ana get in the car at the time.