Harley Davidson Ironwing, 23, is being held on a fugitive warrant from Washington state, WFAA-TV in Dallas reported. Texas police said they don't know how he got there or why.
Ironwing was arrested Tuesday.
"He was with a bunch of people doing drugs. Who knows what brought him here but he came to Fort Worth and now he is going back to Washington in handcuffs," Fort Worth police spokeswoman Tracey Knight said.
Harris-Moore, 22, who is serving a seven-year prison sentence, became one of the most notorious criminals in the country when he went on a crime spree that began in the Pacific Northwest. It ended in the Bahamas when he crash-landed a stolen airplane.
Ironwing became friends with Harris-Moore in school. A CBS report on the pair said that Ironwing, a year older, protected Harris-Moore from bullies and eventually began collaborating with him on burglaries.
A CBS producer who interviewed Ironwing described him as gentle and polite and said he refused to let her buy him meals, although she finally convinced him to accept dinner at a fast-food restaurant.