A 43-year-old Montana schoolteacher last seen six days ago while out on a morning jog has been found dead, her school said Friday.

Sidney Public Schools, for which Sherry Arnold had worked as a math teacher at Sidney High School, announced that the school district learned of her death around 9:30 a.m. Friday.

No other details were immediately available.
Law enforcement officers have taken "one adult male into custody, and another adult male is being questioned" in relation to Arnold's case, the FBI said Friday in a statement.

"The investigation to determine what happened to Ms. Arnold continues," the federal agency said.

Arnold went running around 6:30 a.m. last Saturday in her small town in eastern Montana, but never returned home. Other than one of her running shoes found along her route, authorities had not indicated -- until Friday -- that there had been any sign of her.

The woman's disappearance rocked Sidney, located about 100 miles south of the Canadian border. It has a population of just below 5,200 people, according to the U.S. Census Bureau.
A massive search effort involved hundreds of volunteers, as well as law enforcement authorities and National Guard members.

Authorities on Wednesday "determined the prudent course of action is to scale back the ground search."

"We're such a small community, and crime is absolutely unheard of," said Christine Mullen, 26, a CNN iReport contributor, who joined the search effort, even though she didn't know Arnold personally. "We don't lock our car doors. (We're) completely shocked."

The FBI said Friday that "dozens of tips were called into (a) tip line" -- one of which led to the arrest and questioning.

Sidney Public Schools said that all sporting events for Friday had been canceled and "additional counselors (were) on hand" to help students cope.

On Thursday, the victim's husband, Gary Arnold, told HLN's Jane Velez-Mitchell that he was hopeful that his wife would be found alive. The disappearance has been "very difficult" on the couple's children, though they were trying to stay positive, he said.

"Their mother has raised them well," he said. "They are troupers, they are hanging in there, and they are not giving up hope, either."