Alan Williams resigned as Chicago Bears defensive coordinator last week in part because of inappropriate activity, sources told ESPN's Adam Schefter.

Williams was not involved in any criminal activity, sources told Schefter, but the Bears' human resources department was part of the process that culminated in his abrupt resignation Wednesday.

A digital forensic search was conducted as part of Williams' resignation, according to sources, who added that such a process was part of the team's standard operating procedure.