New evidence suggests the killing of Seattle federal prosecutor Thomas Wales in 2001 may have been the doing of a small group of people and a hired gunman, an FBI official familiar with the investigation told the Seattle Times.

The findings signal a major breakthrough in the 16-year-long investigation, with authorities previously focusing on a single shooter theory involving a Bellevue-area airline pilot as a leading suspect, the Times reported.

Authorities are now investigating the pilot’s relationship with a small group of people believed to be connected to the killing, the official told the paper. The FBI is still pursuing other leads as well.

Wales was 49 years old when he was shot several times while sitting at his computer in his home late in the evening of Oct. 11, 2001. He was working as a white-collar criminal prosecutor in the U.S. Attorney’s Office, the Times reported.

The 57-year-old pilot, who was prosecuted in a fraud case at the hands of Wales, has denied any wrongdoing, according to the paper. He has not been identified because he has not been charged in the case.

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