Suspect Lois Riess. (Minnesota Bureau of Criminal Apprehension)

With her platinum blond hair and a cherubic smile, Lois Riess looks in photos like what she is — a 56-year-old grandmother from small-town America.

And that, authorities say, makes her even more dangerous.

For the past three weeks, police say, Riess has led them on a nationwide pursuit — from the Minnesota worm farm where they found her husband shot to death last month, to Florida, where they suspect Riess befriended and killed a woman who looks like her to steal her identity, and finally to Texas, where police fear she may find her next target.

“She smiles and looks like anyone’s mother or grandmother, but she’s calculating, she’s targeting and she’s an absolute [cold-blooded] killer,” Carmine Marceno, a deputy sheriff in Lee County, Fla., told NBC News after authorities lost Riess’s trail.

Riess and her husband, David, were well known and liked by the 2,000 or so other residents of Blooming Prairie, Minn., according to the Minneapolis Star Tribune. They were regulars for lunch at the local Servicemen’s Club, nearly 100 miles south of Minneapolis. David owned and operated a farm for fishing bait — Prairie Wax Worms.

Concerned that David Riess had not been seen in more than a week, the Star Tribune reported, one of his business partners asked police to look for him.

Officers found him dead of gunshot wounds at the worm farm on March 23, the sheriff of Dodge County told the newspaper. It was unclear how long he’d been dead.

Lois Riess had left town by then. According to the Star Tribune, police suspect she forged her dead husband’s signature before his body was found, transferred nearly $10,000…