By David Schwartz

PHOENIX (Reuters) - A 14-year-old Phoenix boy was arrested by sheriff's deputies on Tuesday for threats made over the Internet to "go on a killing spree" and then commit suicide at his former middle school, authorities said.

The boy was taken into custody without incident at his home after posting the threats in the comments section of a YouTube music video for the hit song "Pumped Up Kicks," said Sergeant Jessie Spurgin, a Maricopa County sheriff's spokesman.

"He gave out a specific place and time for when it would happen," Spurgin said. "That made it a little more credible in our eyes."

Spurgin said a sawed-off shotgun was later found during a search of the boy's north Phoenix home, where he lives with his grandfather. He said investigators were trying to determine if there was a connection between the threats and the weapon.

Spurgin said the boy, who was not publicly identified, has admitted posting the threats on the site.

Sheriff's deputies were tipped off to the ex-Wigwam Creek Middle School student by an out-of-state YouTube viewer who went to the site for "Pumped Up Kicks," by Foster the People.

The lyrics of the catchy top-40 pop single talk of a "cowboy kid" who found "a six shooter gun."

The chorus of the song is: "All the other kids with the pumped up kicks you'd better run, better run, outrun my gun. All the other kids with the pumped up kicks you'd better run, better run, faster than my bullet."

A school district official could not be immediately reached for comment.

Spurgin said deputies were stationed at the school to provide additional security.

(Editing by Steve Gorman, Jerry Norton and Greg McCune)