The upcoming biopic Jackie has found its Robert Kennedy in Peter Sarsgaard (Black Mass). The actor will play Jackie Kennedy’s brother-in-law in the film that follows the former first lady in first four days following the assassination of her husband and the 35th President of the United States, John F. Kennedy. Oscar winner Natalie Portman (Jane Got a Gun) is set to portray the former first lady.

Sarsgaard has been slowly working his way back into the mainstream, appearing in 2013’s Blue Jasmine as well as recent releases Pawn Sacrifice and Black Mass. He’s also set to star in the remake of the classic western, The Magnificent Seven. He also appeared in the NBC miniseries, The Slap. Jackie will be the English-speaking directing debut for Pablo Larrain (No) who is also directing an upcoming biopic on Chilean poet Pablo Neruda.

Sarsgaard previously worked with Portman in 2004’s Garden State which started an impressive run of films for the actor that included the biopic Kinsey and the war drama Jarhead. Sarsgaard will join the ranks of Steven Culp (Thirteen Days), Martin Sheen (TV’s The Missiles of October), and Barry Pepper (TV’s The Kennedys) who all played the former U.S. Attorney General and presidential candidate.

Jackie is currently in pre-production and is set to release in 2017.