Police said Riess started her crime spree in her home town of Minnesota - where she shot her husband, forged his signature to steal $11,000 and made off in his Cadillac Escalade.
Lois Riess, 56, of Blooming Prairie, Minnesota, was last seen Sunday, about 50 miles from Corpus Christi, Texas, heading south on Highway 77, Deputy US Marshal John Kinsey told CNN.
Lois is also a person of interest in the March murder of her husband in Minnesota. That puts her among high-profile offenders considered to be some of the country's most risky individuals. "This was one of her favourites, and she wore it many times", Lohr Stoops told the News-Press.
Dubbed by local authorities as "Losing Streak Lois", Riess is known to have a gambling addiction and often frequents casinos.
Riess has been charged with murder, with grand theft of a motor vehicle, and grand theft and criminal use of personal identification in Florida.
The Dodge County Sheriff's Office has released a surveillance video obtained by investigators from the Kum and Go gas station in Northwood, Iowa in hopes of triggering leads to Lois Riess' whereabouts. Its believed she fled to Fort Myers where she befriended 59 year old Pamela Hutchinson of Bradenton. She moved previous year from Virginia Beach to Florida, where she was killed.
Hutchinson's body was not discovered in the Marina Village condos until April 9.
Lee County authorities have called Riess a "coldblooded killer", and this week USA marshals elevated the search for her to a "Major Case" status.
Added the marshals service: Riess "bears a striking resemblance to (Hutchinson) and has stolen the victim's driver license, credit cards and 2005 white Acura TL (FL tag Y37TAA)".
Prosecutors were preparing second-degree murder charges in the David Riess case. The sheriff's office timeline says that she stopped in Ocala on April 6, just one day after she is believed to have been in the Fort Myers Beach restaurant with Hutchinson. Authorities also said Riess used Hutchinson's ID to make a $5,000 bank withdrawal from a Wells Fargo Bank and withdrew another $500 from Hutchinson's account while she was in Ocala.
Hutchinson's friends said she was visiting Fort Myers Beach to help friends spread the ashes of another friend.
Police tracked Riess to a nearby casino but she had already left by the time they arrived. The vehicle has since been spotted in Louisiana and Texas.