WASHINGTON  - US police have foiled a plot to kill teen pop idol Justin Bieber, legal documents revealed.Mark Staake, 41, and his nephew, Tanner Ruane, were arrested in Vermont and New York last month and face charges in New Mexico of conspiracy to commit murder and conspiracy to commit aggravated battery with a deadly weapon.The pair was allegedly plotting to strangle two victims and castrate them with pruning shears, but a convicted killer who is serving life in prison told police that the “ultimate” target was Bieber, who was performing in New York.“Through follow-up investigation it was discovered that Justin Bieber may have also been a target of the murder plot,” said a statement by New Mexico’s Department of Public Safety. An affidavit detailed the grisly plot, including the brand of pruning shears after the planned murders of two male victims in the northeastern state of Vermont.Staake and Ruane arrived in Vermont by car on November 19 planning to kill their victims - identified only as PL and MS, and referred to as “dogs” - by strangling them with a necktie, the affidavit said.  Dana Martin, who was jailed for life for a 2000 murder in Vermont and who had met Staake in jail in New Mexico, allegedly recruited Staake to carry out the murders. Staake then asked his nephew to help.In a telephone call Martin - who is allegedly infatuated with Bieber - asked Staake what he was going to use to castrate the victims. “Mr Ruane stated that he had brought a pair of hand(held) hedge clippers.”, said the affidavit, which said the shears were made by Durasharp.Martin, who had a tattoo of Bieber on his leg and had tried to contact the singer repeatedly without success, subsequently told police that PL and MS “were not the ultimate targets in the plot. Mr Martin indicated that their ultimate target was JB,” said the affidavit, adding that, when police searched the car they found a pair of Fiskar Durasharp pruning shears and information on their intended victims. Staake and Ruane are currently awaiting extradition to New Mexico, officials said.The 18-year-old Canadian star’s managers said they took Bieber’s safety seriously. “We take every precaution to protect and ensure the safety of Justin and his fans,” a management official told AFP in an email.