GREENEVILLE, Tenn. -

A dozen FBI agents spent Wednesday searching the backyard of a Greeneville home.

We've learned it's connected to a six-year-old home invasion case. Our crew watched as agents used metal detectors in a grid pattern in the backyard at a home on Rainbow Circle.

They would not say what they were looking for, but did say it involved a year-long civil rights investigation.

Back in 2006, we reported that four masked armed men broke into a home on Jim Fox Road; police say they assaulted two men. Deputies chased the men to the home on Rainbow Circle.

The men fled through an upstairs window and a Greene County deputy shot one of them.

FBI supervisory agent Kevin Keithley tells us one aspect of the civil rights investigation includes violations called 'color of law.' "Color of law involves misconduct by police officers in the line of duty," he explained.

The FBI confirms the case involves a 15-year-old boy who was shot. At the time of the shooting, Sheriff Steve Burns said the officer acted appropriately.