Federal prosecutors have obtained another guilty plea from someone linked to an investigation into corruption at Atlanta City Hall.

Shandarrick Barnes pleaded guilty to obstruction of justice by interfering in the investigation. That interference took the form of a brick hurled through the window of Elvin R. Mitchell Jr., a construction company owner who was cooperating with federal authorities.

“The defendant threw a concrete block through the window of E.R. Mitchell’s home, and placed dead rodents on his porch and elsewhere hoping to thwart his cooperation with federal law enforcement,” the U.S. District Attorney’s Office said.

The incident, which occurred in 2015, had the opposite effect, the District Attorney’s Office said.

“Barnes threw the concrete block through Mitchell’s dining room window to get him to ‘shut up,’” said U. S. Attorney Byung J. “BJay” Pak said in a press release. “Instead, that violent act made Mitchell even more resolute in his cooperation with federal law enforcement.  Barnes now faces a significant prison sentence because he decided to obstruct a federal investigation.”

Mitchell told investigators on Sept. 2, 2015 that he had paid bribes to city officials in exchange for contracts.

“On September 11, 2015 at approximately 5:30 a.m., Shandarrick Barnes threw a concrete block with the words ‘ER, keep your mouth shut!’ written on the side, through a plate glass window in Mitchell’s home,” the U.S. Attorney’s Office said. “When Mitchell emerged from the house to see who had thrown the block, he saw that dead rats had been placed on his porch, car and in his mailbox.”

Barnes later admitted to throwing the brick in an interview with the FBI and IRS.

“He said he was livid and his decision to throw the brick through Mitchell’s window was motivated by his desire to hinder Mitchell’s communication with agents concerning possible tax violations,” the U.S. Attorney’s Office said. “He said he felt that Mitchell’s communications to federal law enforcement would negatively affect his employer’s businesses.  Barnes was concerned that the communication with agents was detrimental to obtaining other business that he and others were actively seeking at that time.”

Barnes will be sentenced in February.

The corruption investigation has rattled city hall and seeped into the city elections, which are occurring today, Nov. 7.

Last month, Mitchell and another contractor, Charles P. Richards, Jr., were sentenced to prison terms for paying bribes to city officials.