CBS Films and Lionsgate have tapped “Supergirl” star Melissa Benoist, Khandi Alexander and Jake Picking to join Mark Wahlberg’s “Patriots Day

The Boston Marathon bombing saga includes John Goodman, J.K. Simmons, Michelle Monaghan, Kevin Bacon, Jimmy O. Yang, Vincent Curatola, Alex Wolff, James Colby and Rachel Brosnahan in its cast.

The film is directed by Peter Berg and produced by Scott Stuber, Mark Wahlberg, Hutch Parker, Dylan Clark, Stephen Levinson, Dorothy Aufiero and Michael Radutzky.

Benoist is playing Katherine Russell, widow of deceased Boston Marathon bomber Tamerlan Tsarnaev. Alexander is playing a law enforcement interrogator and Picking is playing MIT Police Officer Sean Collier, who was slain during a late-night confrontation with Tamerlan Tsarnaev and his brother Dzhokhar Tsarnaev, four days after the bombing.

“Patriots Day” is currently shooting in Boston.

The film is being co-financed by CBS Films and Lionsgate with the former handling production and marketing and the latter handling distribution. “Patriots Day” will open Dec. 21 in Boston, Los Angeles and New York.

UTA and Anonymous Content represent Benoist. Alexander is represented by Green & Associates. Innovative Artists and Management 360 represent Picking.