'Mean Girls' star demands 'justice' for relative's brutal murder after discovering harrowing family secret

"Oh, my God! What?!" Seyfried said as she read a newspaper article from the time, putting her hands to her forehead in disbelief. 

"John P. Ebert, the well-known retired baker, a good citizen and an inoffensive man, was shot three times by an unknown assailant on the back step of his home at Washington and Lumber Streets at 9:30 [p.m.]," the article read. 

Seyfried, 39, continued to read out loud, "He had just about reached the back door ... when, from between the outhouse and a grape arbor which screens it stepped a man who fired three shots at him point-blank."

Henry Louis Gates Jr., the show's host, confirmed, "Your third great-grandfather was murdered."

He then asked the actress, "Have you ever heard this story before?"

"Nope, no. Definitely no," Seyfried replied.

She then added how she felt terrible for her third-great grandmother, who was also named Amanda, and their children. 

"It's weird - I don't know him, but yet, he's family," Seyfried said in the dramatic video clip. "I'm just like, 'How dare they!' . . .  'Find justice.'"

The actress was shocked to discover that she actually is not a "Roberts" and was told her last name was drastically different.

The historian revealed that Julia's great-great-grandmother had an affair with a married man after her husband Willis Roberts' death. Gates Jr. said that Henry McDonald Mitchell Jr. was the name of her biological great-great-grandfather.

He added that Mitchell had six children of his own.

"So, we're Mitchells?" the "Pretty Woman" actress asked at the time.

"You're Julia Mitchell," Gates Jr. confirmed. "You are not a Roberts, biologically."

"Wow. . . . On the one hand . . . truly . . . my mind is blown," Roberts emotionally responded to the scandalous revelations.