After working as a California Highway Patrol officer from 1971 to 1986, Walls met Sierra president Ken Williams, who wished to create an adventure game in the police procedural genre.

After leaving Sierra in the early 1990s, Walls joined several other game developers, including Tsunami Media in 1992 and Westwood Studios in 1996, before retiring in 2003.

Though he survived the incident, he began to experience post-traumatic stress symptoms, and in 1985, was placed on administrative leave to evaluate his condition.

[1][4] While still on administrative leave in 1985, Walls' then-wife Donna, who was a hairdresser in Oakhurst, introduced him to Ken Williams, co-founder and then-president of Sierra On-Line.

Williams asked Walls to condense his experiences in the CHP into a short story, preferably around two pages long.

After leaving Tsunami Media, Walls contracted with two other companies—Tachyon Studios and Philips Interactive Media—for games that would ultimately never see release.

He was subsequently offered a full-time design position, working on Pirates: The Legend of Black Kat and Earth & Beyond, both released in 2002.

In 2003, Westwood Studios was bought out by Electronic Arts and merged into EA Los Angeles, with most employees, including Walls, let go as part of the company's acquisition.

[1] On February 2, 2013, during a podcast hosted by Chris Pope, Walls announced he had plans to develop a successor to Police Quest, using Kickstarter for funding.