Manhunt widens as US Marshals boost reward to $16K for Florida murder suspect on the run

A reward of up to $16,000 is now being offered for information leading to the arrest of a Florida murder suspect as investigators continue searching across multiple states for a woman accused in the death of a Niceville man.

The new total includes an additional reward offered by the U.S. Marshals Task Force on Tuesday, along with previously announced rewards from Emerald Coast Crime Stoppers and the Florida Sheriffs Association Criminal Apprehension Assistance Program.

The Walton County Sheriff's Office said Isabelle Johnson, 38, is wanted on an active warrant for an open count of murder in the death of Jason Christopher Coulthart, 43. Johnson remains at large and is considered dangerous, according to investigators. Authorities have said law enforcement agencies in Florida, Georgia and Alabama are actively searching for her.

Coulthart was reported missing to the Niceville Police Department on May 24 after he was last seen leaving the College Condominiums on East College Boulevard. During the investigation, detectives developed information identifying a property off Sunset Lane in Freeport where Coulthart's body had allegedly been buried. Niceville police then notified the Walton County Sheriff's Office, which has jurisdiction over the property.

A search warrant was executed June 25, and investigators discovered human remains buried in a shallow grave on the property. DNA testing later confirmed the remains belonged to Coulthart.

Since the investigation began, five people have been arrested in connection with the case.

WCSO announced Bobbi Wagstaff, 31, was charged with accessory to capital murder after the fact and possession of methamphetamine. Martin and Sandra Leaverton, both 63, were charged with accessory after the fact to capital murder after investigators alleged they helped Johnson by retrieving her belongings, providing a cellphone and attempting to help her find refuge outside Florida.

The sheriff's office said Michael Ray White, 74, and Kathleen Morris, 59, were later charged with accessory to a capital felony after the fact and obstruction after authorities said they provided Johnson shelter, transportation and supplies while misleading deputies about her whereabouts.

Sheriff Michael Adkinson previously said investigators are working to hold everyone involved accountable.

"The next step in this investigation is to hold every single person involved in Jason's death accountable," Adkinson said.

If they knew, if they helped, or if they chose not to speak up, they will have to answer for their role in this."

Investigators said Johnson has ties to the Freeport area, Georgia, and Alabama may be using multiple identities to avoid capture. She is known to use several aliases, including Harley, Jessica Elaine Bowman, Jessica Elaine Thrush, Jessica Elaine Trash and Jessica Dowdy. Authorities describe her as a white female approximately 5 feet 3 inches tall and 120 pounds with brown hair and hazel eyes.

The Walton County Sheriff's Office recently warned that Johnson may have changed her appearance in an effort to evade arrest and urged anyone with information about her whereabouts to come forward.

Anyone who sees Johnson is urged not to approach her and to call 911 immediately. Anyone with information can contact the Walton County Sheriff's Office at 850-892-8111 or Emerald Coast Crime Stoppers at 850-863-TIPS (8477).