Glen Mazzara and Julie Plec both fail to recall Shannon Richardson's involvement with their respective shows.

Glen Mazzara and Julie Plec both fail to recall actress Shannon Richardson's involvement with their respective shows.

Following news Friday that Richardson was arrested and charged with mailing a threatening communication to the president of the United States, the executive producers behind a pair of shows the suspect apparently appeared on have one question: who?

Multiple outlets, including The Hollywood Reporter, ran stories identifying Richardson as a Walking Dead actress who also appeared on The Vampire Diaries. Only the actress had minor roles in both series.

STORY: 'Walking Dead' Actress Arrested in Connection to Obama, Blomberg Ricin Letters

Richardson was arrested in connection with the ricin-laced letters mailed to President Barack Obama, New York City Mayor Michael Bloomberg and Mark Glaze, a gun control advocate in Washington, D.C., last month.

On AMC's zombie drama, Richardson had a nonspeaking role as a glorified extra -- a member of the undead (aka a walker) -- in two episodes of the first season of the series. And it's a similar case on The CW's The Vampire Diaries.

The wave of headlines led former Walking Dead writer/executive producer Glen Mazzara and Vampire Diaries showrunner Julie Plec to take notice.

"Some actress from TWD sent ricin letters to the Prez? Never heard of her. Anyone know what role she played?" Mazzara wrote on Twitter.

Answered Plec shortly afterward: "If she played an equivalent part to one she supposedly played on TVD, she was third background from the right. Or something." Earlier, she tweeted: "My mom called me today very concerned about my affiliation w ricin terrorists. She's not hip to the term click-bait. Nor was I until today."

The 35-year-old Richardson was arrested in Mt. Pleasant, Texas, on Friday and appeared in front of Judge Caroline Craven on Friday afternoon in Texarkana, Texas, for an initial appearance. She was charged with mailing a threatening communication to the president of the United States. If convicted, Richardson faces up to 10 years in federal prison.

Richardson -- also known as Shannon Rogers and Shannon Guess -- has an IMDb page under the latter name with several photos and a handful of videos -- yet no official credits.