Amanda Seyfried learns shocking truth about third great-grandfather's death

Amanda Seyfried is shocked.

The actress just uncovered a shocking piece of her family history on the season 11 premiere of PBS' Finding Your Roots. 

In an exclusive clip shared by PEOPLE, the Mamma Mia! actress learns about the tragic fate of her third great-grandfather, John P. Ebert, who was murdered in 1905.

As host Henry Louis Gates Jr. guides her through the discovery, Seyfried, 39, reads aloud from an old newspaper article, “He has 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.”

The article describes Ebert, a retired baker and respected community member, as "a good citizen and an inoffensive man." 

The shocking murder occurred at 9:30 p.m. near his home at Washington and Lumber Streets.

Visibly moved, Seyfried reacts, “Oh my God, that’s so sad.” Gates confirms, “Your third great-grandfather was murdered.”

When asked if she had any prior knowledge of the incident, Seyfried responds, “Nope, no. Definitely no.”

The discovery evokes a mix of emotions for the Emmy-winning actress. 

“It’s weird — I don’t know him, but yet, he’s family,” she reflects, adding, “I’m just like, ‘How dare they!’ Like, ‘Find justice.’”

Seyfried is one of several celebrities featured in the newest season of Finding Your Roots, which delves deep into the ancestry of its guests. 

Other notable participants this season include Joy Behar, Kristen Bell, Laurence Fishburne, Debra Messing, Dax Shepard, Sharon Stone, Chrissy Teigen, Amy Tan, and Sheryl Lee Ralph, among others.