Rachel Brosnahan and Christopher O’Shea are the latest additions to Patriots Day, the CBS Films and Lionsgate pic about the events surrounding the Boston Marathon bombing. They will play Jessica Kensky and Patrick Downes, newlyweds who were at the finish line to cheer on runners the day of the attacks. Both were seriously injured but survived, and their inspiring love story touched many.

“The survivors are the heart of this story, and Rachel and Christopher are bringing their immense talents and their respect for Jessica and Patrick’s extraordinary courage to the film,” director Peter Berg said.

Production is under way on the pic, which also features Mark Wahlberg, Kevin Bacon, John Goodman, J.K. Simmons, Jimmy O. Yang, Vince Curatola, Michael Beach and James Colby. Bridge of Spies Oscar nominee Matt Charman penned the script. Scott Stuber, Wahlberg, Hutch Parker, Dylan Clark, Stephen Levinson, Dorothy Aufiero and Michael Radutzky are producing. CBS Films is handling production and advertising for the film, which Lionsgate plans to release December 21.

Brosnahan starred on WGN America’s Manhattan and will star in Woody Allen’s upcoming Amazon comedy series. She also recurred on House of Cards and did an arc on The Blacklist. Next up are the features Boomtown and The Fixer. She’s repped by Innovative Artists, Carole Dibo Talent Management and Schreck Rose. O’Shea, who has appeared on Madam Secretary, Point of Honor and Baby Daddy, is with Innovative, Haven Entertainment and Todd Rubenstein.