With her platinum blonde 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, Ms 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 Ms 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-blood killer,” Carmine Marceno, a deputy sheriff Lee County, Florida, told NBC News in Florida, after authorities lost her trail.

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

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

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

Ms Riess had left town by then. According to the Minneapolis Star Tribune, police suspect she forged her dead husband’s signature before his body was found, transferred nearly $10,000 (£7,000) into her account and headed to a casino across the Iowa border.

NBC News reported Ms Riess had a gambling addiction.

She had left Iowa by the time police tracked her there in late March, the Minneapolis Star Tribune wrote. State officials began to post her photos on Facebook, urging anyone who saw her to call 911 and not go near her, as she was believed to be armed and dangerous.

From Iowa, police believe, Ms Riess drove to Lee County, Florida. There, they said, she met a woman named Pamela Hutchinson, 59, with a similar shade of light-blonde hair.

“She befriended this woman. The woman probably gave her some sob story,” Ms Hutchinson’s cousin Daniele Jeffreys later told WTVR. “My cousin went out helping the world... She’s just giving to a fault. To her death.”

On 5 April, the two women were recorded on surveillance camera at the Smokin’ Oyster Brewery in Fort Myers, sharing a laugh.

According to the Minneapolis Star Tribune, another surveillance camera photographed Ms Riess at Ms Hutchinson’s condo in the same city.

On 9 April, police found Ms Hutchinson shot to death at her condo in the same city. Another surveillance camera photographed Riess at the building. Ms Hutchinson’s uncle told WTVR she’d been shot through the heart.

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The dead woman’s purse had been emptied out, sheriff’s investigators said. Her identification, credit cards and car keys were gone. So was her car.

The search for Ms Riess was now a multistate and federal matter. More public advisories went out, with more photos of the grandmotherly woman and the car she was believed to be travelling in, which was now the car of the woman police think she killed.

The vehicle was spotted near Corpus Christi, Texas, this month, Florida authorities announced at a news conference last Friday. Her current whereabouts are unknown.

The obituary for Mr Riess was published last week and mentioned his children and grandchildren, but not his wife.

“Pure evil,” Ms Hutchinson’s cousin told WTVR. “That’s really the only thing that could resonate with my system... it’s just evil that flowed through.”

In Florida, the deputy sheriff told NBC he had never seen a killing like it. “This is the first time in my career I’ve seen someone steal someone’s identity and target them for the way they look in order to murder them,” Mr Marceno said.

And he worries it won’t be the last.

“I suspect Riess at some point in time will have no resources and she will become more desperate,” Mr Marceno said, “and may kill again”.