Law enforcement officials are trying to find a 20-year-old man who they say has been picking out people at random and terrorizing them at gunpoint in a rash of street robberies and carjackings in the Twin Cities since early last year.

The latest charges filed Tuesday in Hennepin County District Court against Ricardo Rydell Walker, of St. Paul, say he robbed two victims as they walked in a parking lot near Augsburg University in Minneapolis shortly before 5 a.m. in one of three violent incidents June 28.

About two hours later outside a West St. Paul apartment complex, Walker and an accomplice allegedly drove up next to another vehicle and got out. One of them put a gun to one victim's cheek and robbed him of his cash and credit cards. They also demanded the PIN for his bank card "or he would kill him," the robbery charges read.

That same morning just west of the University of Minnesota campus, Walker and another suspect approached a man on foot, hit him in the head with a gun while he was on the ground and took his wallet, the charges read.

Eight days later, on July 6, Walker and his accomplice pulled off a similar robbery in West St. Paul and was arrested later that morning, according to charges.

Prosecutors in three counties — Dakota, Ramsey and Hennepin — now have active warrants out for his arrest.

Walker's penchant for armed robbery began in February 2021, less than two months after he turned 18. Within a year, one criminal complaint read, officers said they were "well-acquainted" with Walker and at least one of his accomplices for "having been involved in numerous robberies/carjackings. [They] were known to display firearms and known to target expensive vehicles."

In December 2021, Walker was civilly committed in Ramsey County District Court as mentally ill and chemically dependent. That put his criminal cases on hold as he entered the Anoka Metro Regional Treatment Center.

He was then moved to a less restrictive sober house in St. Paul on Dec. 19, shortly before the latest criminal complaints and warrants for his arrest were filed.

According to charges in various complaints:

Feb. 10, 2021: Walker and a second man carjacked a woman's BMW in the 600 block of Palace Avenue in St. Paul.

Feb. 11, 2021: Walker carjacked a sedan at gunpoint in the 1500 block of Goodrich Avenue in St. Paul and took his victims' wallets and a cellphone. He was soon arrested under a walkway near the Hmong College Prep Academy on Brewster Street. Prosecutors believe Walker and a woman arrived at the robbery scene in a car they had stolen earlier that morning.

May 23, 2021: A 62-year-old woman was robbed of her purse by Walker outside her home in the 1900 block of Beechwood Avenue in St. Paul. Walker was spotted on video surveillance using her credit cards.