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.
"Ms. Hutchinson was targeted by the suspect due to the similarities in their appearance," Marceno said Friday during a news conference.
In describing an April 9 search of Hutchinson's condo, he said, "Ms. Hutchinson's purse was found to be in disarray and all cash, credit cards and identification appeared to have been removed."
"Riess' mode of operation is to befriend women who resemble her and steal their identity," Marceno said, calling Riess a "dangerous fugitive."
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)."
"Riess is considered armed and dangerous and should not be approached," Marceno said Friday.
Surveillance video shows Riess talking with Hutchinson on the evening of April 5 at a brewery restaurant in Fort Myers Beach, according to the Lee County Sheriff's Office, which released the images.
Hutchinson "was a friend to everybody," her cousin, Daniele Watts Jeffreys, told HLN's Ashleigh Banfield. "She's never met a stranger. She's just an open, welcoming woman."
Hutchinson had rented a condo in the seaside town as part of trip centered on spreading a relative's ashes in the area, Jeffreys said.
"It's actually a triple tragedy," Jeffreys said, referring to the purpose of her cousin's trip and her death. "Pam should have left the day before, and that would have actually had her alive. She stayed an additional day."
CNN's Hollie Silverman, Jeremy Ryan and Michelle Krupa contributed to this report.