Police say in a statement released Thursday that the investigation stems from an arrest that occurred early Saturday morning in the Temple Street courtyard.
Police said the FBI also looked into the issue before deciding it was best handled by local authorities.
Authorities did not immediately provide additional details, including the name of the sergeant and the alleged misconduct.
CHARLESTON, W.Va. -- A federal judge would not dismiss an excessive force claim in a lawsuit against a Charleston Police SWAT officer accused of kicking a woman several times as she lay face down on the floor of her home.
Last week, U.S. District Judge Joseph R. Goodwin denied a motion to drop an excessive force claim against the SWAT officer, who is identified in court documents only by the last name "Kapeluck."
The original lawsuit alleges that in October 2010, Kapeluck was part of a 10-man search warrant raid, which included a team of three snipers, at the Charleston home of Ludie Perdue and her sons Joshua and Joseph on 1031 Aspen Road.
Search warrants had been issued for Joshua and Joseph Perdue on charges of entering without breaking and also on receiving and transferring stolen goods. Ludie Perdue also had a warrant for receiving or transferring stolen goods, but according to a SWAT deployment report, the team's primary targets were Joshua and Joseph Perdue.
The SWAT team was requested because of the Perdues' criminal history, which included previous charges of carrying a concealed weapon, brandishing and wanton endangerment, the deployment report states. A detective saw weapons at the home prior to the raid, according to the report, which lists the warrant as "high risk."
At about 10:30 a.m., the team broke into the home by using a tool to disable the door's lock cylinder, and then set off a flash-bang grenade near the point where the team entered the home.