Police try to determine uncle's motive for taking niece

This undated photo provided by the Tennessee Bureau of Investigation shows Gary Simpson. Officials have reported Thursday, May 12, 2016, that Simpson has been arrested in connection with the abduction of his niece, Carlie Marie Trent, 9, of Rogersville, Tenn. Both Trent and Simpson were reported to have been found together north of Rogersville. (Tennessee Bureau of Investigation via AP) (The Associated Press)

In this arrest photo made available by the Hawkins County Sheriff's Office, TN., shows Gary Lewis Simpson, 57, on Friday, May 13, 2016. Simpson was arrested and charged with aggravated kidnapping of his 9-year-old niece. (Hawkins County Sheriff's Office via AP) (The Associated Press)

Authorities are trying to determine why an East Tennessee man charged with aggravated kidnapping disappeared for more than a week with his 9-year-old niece.

Tennessee Bureau of Investigation Director Mark Gwyn told news outlets that Gary Simpson is being interviewed to determine what transpired over the last eight days.

Two men searching the back country of northeastern Tennessee on Thursday found Carlie Trent, who had been missing since Simpson signed her out of school May 4.

Gwyn said Donnie Lawson and Stewart Franklin were acting on law enforcement appeals to search isolated areas on all-terrain vehicles when they found the two in a barn. Franklin held Simpson at gunpoint while Lawson went to call police.

Gwyn said there were no indications that Carlie was harmed, but she was being checked as a precaution.