>> we sensed they were related, but knowing and proving that they are related are two different things. the rear of this parking lot provides a very good area, take a shot, one shot, one loud shot, one fatal shot and then move away without causing a great deal of distraction. >> a witness reports seeing a white box truck fleeing the scene. it's the first material clue for investigators. >> the investigation really, really took on speed right here. >> an hour and 20 minutes later, five and a half miles away, lori ann lewis at rivera has stopped at a self-service vacuum stand to clean out her minivan. >> everyday people doing everyday things usually are not the victims. >> rivera, mother of a young daughter, is just 25 years old.