"There are general reports written on Mr. Barr where he threatened residents on a fairly regular basis and these threats also included staff on a few occasions," Rubenstein wrote in his letter to Circuit Court Judge Thomas W. Steptoe Jr.
"Some of his comments were, `If I'm not allowed to say my piece when I'm upset I'm afraid I'll beat a CO (correctional officer) to death,''' Rubenstein wrote in the letter, which is filed in Morgan Count Circuit Court.
In addition to the Jan. 30 slaying of the truck driver, Barr, 20, and his half brother, Alan Chauncey, 28, of Ranson, W.Va., also were charged in the Feb. 11 rape of two women and with slashing the womens' mother's throat in Conway, Ark.
Chauncey and Barr each were charged with rape, kidnapping and car theft in that case, police said.
"His threats of violence made it virtually impossible to deal with him in a minimum security setting such as Anthony Center," Rubenstein said in his letter.
The Anthony Center houses offenders between 18 to 23 years of age who appear to be appropriate candidates for rehabilitative programs not requiring close confinement.
Despite his brush with the law and his problems at the Anthony Center, some police and school officials who knew Barr said he could be polite and they felt he had the potential to be a productive member of society.
At the Anthony Center, Barr received a General Equivalency Degree, and passed carpentry, blueprint reading and social skills classes, Rubenstein wrote.
Barr and Chauncey were ordered to undergo mental evaluations at a mental institution in Little Rock, Ark., following their arraignment on capital murder charges in the slaying of truck driver Arthur Joe Cotton near Morrilton, Ark.
Rubeinstein said Barr would try to hurt himself by doing things such as beating his head. He also would beat buildings with his fists, Rubenstein wrote.
Barr was sentenced to a year in the Eastern Regional Jail near Martinsburg, W.Va., after he was removed from the Anthony Center, said probation officer Dennis Barron.