Walker Browning was a computer programmer for Springbok Electronics, employed in creating data disks for Global Positioning Satellite units. He was fired in or around October 2002.
Going to a baseball game on an invitation from his friend, Browning happened to be the fan who caught a baseball hit by star player Darryl Grant, marking the new record for home runs hit in a single season. The ball, a "little piece of history," was therefore worth around $3 million.
After losing his job, Browning decided to sell the baseball, but by then, Scott Gregorio was closing in on Grant's record, and there were no buyers. Browning panicked and tried to put Gregorio out of action by attacking him with a baseball bat as he was leaving the stadium. But that didn't work, and Gregorio was thereafter assigned a pair of bodyguards by the team.
But by following Gregorio around, he learned that he was having an affair with Erin Hammond, the wife of billionaire Lawrence Hammond. So he broke into the parking garage of Lawrence Hammond's office, and planted a homemade disk in his car's GPS device that would guide the Hammonds to a deserted parking lot, where Browning lay in wait. As soon as they stopped, Browning approached and shot both Hammonds. Erin died first, while Hammond, whom Browning shot only once, before Browning ran him over with his car, lingered long enough to give a clue to the killer's identity.
As Browning hoped, grief over Erin's death sent Gregorio into a slump, and he eventually failed to break the record. But Browning was identified by Adrian Monk, and arrested by the SFPD before he could sell the ball. In the fracas in his home with his guard dog, Toby, the $3 million baseball was destroyed.
Walker Browning aparently knew some German, as he gave Toby a command to get the ball in German.