Washington (CNN) As a 43-year-old youth counselor from Sacramento, California, Brian Dempsey certainly did not fit the traditional profile of someone likely to travel to Syria in hopes of joining ISIS -- but his journey is helping shed new light on why some Americans decide to fight alongside extremists in combat zones on the other side of the world.

Dempsey is one of 64 Americans whose experiences in Iraq and Syria were profiled as part of a new report released Monday by the Program on Extremism at George Washington University.

After working as a youth counselor for the California Department of Corrections and Rehabilitation for over a decade, Dempsey converted to Islam sometime between 2011 and 2013 before initially traveling to Syria in 2013 to "participate in combat," according to the report and court documents.

His journey and subsequent arrest while attempting to return to the US highlight a wide range of American residents who have traveled to Iraq and Syria and successfully associated with or joined a an extremist group since 2011.

The cases outlined in the report include one-third of the at least 153 Americans who have been arrested on ISIS-related charges Since 2011.

At 43 years old, Dempsey is one of the oldest individuals mentioned in the report -- which found the average age of those Americans who traveled to Iraq or Syria to be 27.

More than 89% of the individuals mentioned were men and 70% were American citizens or permanent residents.

"Two travelers were granted refugee status in the US before departure, and another was studying in the US under a student visa," the report said. "Sixteen cases (25%) involved an individual whose residency status could not be determined."

While the vast majority of Americans who sought to join violent extremist groups abroad either died overseas or remain unaccounted for, the report notes that 19% of the individuals mentioned were -- like Dempsey -- apprehended in the US or overseas.

According to criminal complaints, Dempsey conspired to travel to Syria with an individual referred to as "Person A."

"Person A" also converted to Islam but his path to Syria is considered "unusual," according to the report, given what the authors believe to be his past association with a "sovereign citizen" group primarily geared toward protesting tax laws.

The authors of the report understand this individual was released from prison in 1999 after serving four years for several counts of fraud and crimes connected to an assault on a county government employee.

"Given the lack of publicly available evidence about these cases, it is especially hard to determine how a former correctional officer and a former 'sovereign citizen' who both converted to Islam met one another, and decided to travel to Syria to fight," the report said. "However these cases are reminders that the social connections that influence travelers are not always straightforward or conventional."

The two men took very different paths once they arrived in Syria as Dempsey attempted to return to the US after only a month and a half but "Person A" remained in the region -- likely joining ISIS or another extremist group and his current whereabouts remain unknown, according to the report and court documents.

Despite only spending a short time in Syria, Dempsey was placed on the FBI no-fly list and questioned by investigators after he attempted to return to the US via Rome, Italy in August 2013, the authors of the report claim.

During that first interview, Dempsey claimed he traveled to Syria with "Person A" to "help refugees" and said he did not know any members of terrorist organizations, the report and court documents said.

Dempsey canceled his return trip to the US and stayed in Rome following his initial interview with investigators but was questioned again by the US government in January 2014 -- at which time he admitted to traveling to Syria to fight and acknowledged contact with several extremist organizations, including ISIS, according to the report and the criminal complaint.

He also admitted to engaging in combat on two occasions, the report said, citing the court documents.

Dempsey fled Rome in October 2014 and was arrested in the UK in January 2017 on charges of making false statements to FBI investigators. He is awaiting extradition to the US, according to court documents.

While the length of sentences for terror-related crimes tend to vary in the US, if convicted Dempsey faces a maximum of sentence of eight years in prison or a fine up to $250,000, court records show.

According to a January 2017 court filing by his lawyer, Dempsey "does not waive any of his rights under either the Fourth Amendment, Fifth or Sixth Amendments to the US Constitution and refuses to provide any statements or permit any searches with any one from any branch of law enforcement in connection with any such actions involving questioning, investigation or searches."

'While smaller in number than most Western countries, America has not been immune to phenomenon of foreign fighters," said Deputy Director of the Program on Extremism at George Washington University Seamus Hughes, one of the authors of the report.

"They come from all walks of life, most using personal connections to make the journey. The lessons learned ... should serve as a basis to understand the current threat and prevent a next wave of recruits,'" said Hughes, an expert on terrorism, homegrown violent extremism and countering violent extremism.

The chairman of the Joint Chiefs of Staff, Gen. Joseph Dunford, said in October that "as many as 40,000 foreign fighters from 120 different countries" had joined ISIS in Iraq and Syria.

President Donald Trump has often touted US military gains in Iraq and Syria and said ISIS is "on the run" as their territory continues to shrink.

American foreign fighters have explored other areas as potential destinations -- including Yemen, Libya, Somalia, and Nigeria -- but those cases were not specifically included in Monday's report.

Sentences for terror cases similar to Dempsey's have typically ranged between 10 and 15 years but given most of those individuals were typically younger in age, most will be released and be allowed to continue to live in the US.

"There is a real question of when you put someone in jail, is that the best spot to put them for some of these crimes and how long sentences should be," said David Sterman, a policy analyst at New America who focuses on homegrown extremism.