After three decades of working the beat, one of Minnesota's top cops is calling it quits.

Dave Bjerga, a longtime Bureau of Criminal Apprehension (BCA) agent, will retire on Tuesday after nearly 32 years of investigating cases from Bemidji to St. Paul.

"It's time," Bjerga, 55, said.

Bjerga started his career in 1981 as a deputy and investigator in Crow Wing County. After joining the BCA, he worked his way up from field agent to head of the agency's northern Minnesota office and then to assistant superintendent in St. Paul, where he briefly served as interim superintendent.

Among his high-profile cases: the 1999 killing of Katie Poirier, a 19-year-old Moose Lake convenience store clerk, and the 2003 murder of Dru Sjodin, a 22-year-old college student in Grand Forks, N.D.

But it's the unsolved cases that haunt: the 2001 murder of Pine River liquor store clerk Rachel Anthony, 50, and the disappearances of Jacob Wetterling, 11, and LeeAnna Warner, 5.

"You don't remember the successes," Bjerga said. "You only remember the ones you didn't solve."