“It’s Baltimore — don’t be surprised by anything that takes place here,” we’re warned early on in “The Slow Hustle.” The HBO doc sees Sonja Sohn, best known for her portrayal of Detective Kima Greggs on “The Wire,” returning to Charm City. Here, the “Baltimore Rising” director investigates the 2017 death of Sean Suiter, a detective who was shot in the head while in the line of duty. Early on, loved ones suspected foul play. “For days, this investigation operated on a false assumption,” we’re told. “New information” revealed that Suiter was set to testify against eight elite Baltimore officers the very next day. This bombshell led to more concerns about the Baltimore police department, which is described as “one of the most corrupt police forces in the country.” As one character explains, “There’s a lack of trust in this department and its ability to tell the truth about an investigation.” So when they claimed that Suiter’s death was a suicide, far from everyone was convinced.

Even with that initial warning not to be surprised by anything and a growing chorus of voices emphasizing just how corrupt the police department is, “The Slow Hustle” paints a damning — and yes, shocking — picture. Though Suiter’s death and the circumstances surrounding it are the main focus of the doc, Sohn is using the case as a springboard for asking big questions about law and order, and the politics that inform them. The handling of Suiter’s death prompts one journalist to say, “Black lives really don’t matter, even if you’re a police officer.”

“At this point, I can say the one question I would like to see discussed is: What happens when the public can no longer trust its police department? How does that reverberate outwardly to its residents beyond the police brutality and civil rights violations that contribute to the creation of that erosion of trust and, ultimately, impact the department itself? Sohn told us.

“The Slow Hustle” premieres tonight at 8 p.m. ET on HBO/HBO Max.