A California man has been charged with sending a threatening letter to a conservative podcaster and a close associate of political influencer, Charlie Kirk. According to federal court documents obtained by CBS 8, San Diego resident George Isbell Jr., 69, was charged with sending threats in the mail to the Florida man's home in Tampa following Kirk's murder. In the complaint, federal investigators say Isbell previously had been under investigation for sending at least one other threat to a Louisiana politician in 2021. The investigation began after the wife of Benny Johnson, a close friend of Kirk, received a letter at the couple's home. CBS 8 is the local source for San Diego breaking news and top story headlines. Get the latest local San Diego TV news, sports, weather and more. More from CBS 8: Website: https://www.cbs8.com Twitter: https://twitter.com/CBS8 Facebook: https://www.facebook.com/News8 Instagram: https://www.instagram.com/cbs8