|Last appearance:||Santabarbaratown 2|
Jack Atwater was a retired SBPD police officer and one of Henry's old friends, before Henry discovered Jack, along with other retired cops (and old friends) Lou Gamble and Jerry Carp, was helping covering up an illegal business run by Ellis Beaumont. Jack was threatening Shawn with phone calls and pictures of his girlfriend Juliet, designed to demonstrate her vulnerability, before Henry caught and arrested him. After Jerry shot Henry, Jack agreed to cooperate with the police to catch Jerry, but was shot and killed by a sniper working with Jerry. He is portrayed by Jerry Wasserman.
In "Santabarbaratown", Shawn, Gus and Henry begin looking into a case which revealed that Lou Gamble was involved in hiding illegal activities being committed by Ellis Beaumont, such as helping him dispose of Veronica Town's body, and hiding his drug manufacturing business. Shawn then starts to receive ominous phone calls, warning him to stay away from the case, and pictures on The Blueberry's windshield of Juliet, with a big red X through one.
Shawn continues to investigate, but as he's walking to Juliet's house, he's attacked and punched in the face. Shawn and Gus go to confront Ellis's son Jordan, who they believe is responsible, however they get another threat from the caller, and run to the phone where it came from- a payphone. They spot one of Henry's old partners across the street, and give chase, but he begins to escape before Henry stops and arrests him. Jack says that he needed the money, and brought in Lou because he knew he needed the money too. Beaumont had made them help cover up Veronica Town's murder or else he would've tipped off the chief. Lou began to crack, so he threatened him and his wife, much the same as he did to Shawn and Juliet. Henry thinks he murdered Ellis Beaumont, but he insists he didn't, and Shawn realizes who did and rushes off to arrest her, while Jack is taken into custody.
In "Santabarbaratown 2", Shawn and Gus are chasing after Jerry Carp, because he shot Henry. They think that he owns a shooting range, where Shawn begins shooting things like crazy to try to get Jerry called, however it is revealed that Jerry doesn't own the shooting range, but Jack does. Shawn and Gus go to ask him some questions, and he agrees to cooperate, as he'd never want to hurt Henry, but as he's being transferred he's shot by a sniper working with Jerry, killing him.