FBI Special Agent in Charge Richard DesLauriers is assigned to investigate the bombings in collaboration with Boston police commissioner Ed Davis, while Tommy searches for evidence and helps people that have been injured or separated from their loved ones in the chaos, including Patrick, Jessica, Steven, and Leo.

FBI analysts review footage of the bombing and identify Dzhokhar and Tamerlan as suspects, but DesLauriers is reluctant to release their pictures to the public without further evidence.

His hand is forced when the pictures are leaked to the press, while Watertown Police Sergeant Jeffrey Pugliese's men begin conducting door-to-door searches for the pair.

The Tsarnaev brothers kill Massachusetts Institute of Technology Police Department officer Sean Collier in a failed attempt to steal his pistol, and then carjack student Dun "Manny" Meng, telling him that they committed the marathon bombing and planned to conduct another one in New York City.

Meanwhile, Tamerlan's wife Katherine Russell and Dzhokhar's college friends from UMass Dartmouth (Dias Kadyrbayev, Azamat Tazhayakov, and Robel Phillipos) are detained by the FBI Hostage Rescue Team and questioned by the High-Value Interrogation Group.

Russell refuses to disclose any knowledge of her husband's illegal activities, paraphrasing the Quran in defiance, while Dzhokhar's roommates appear oblivious to his plans, despite having earlier found bomb components in his possessions.

Later in Watertown, local resident David Henneberry realizes Dzhokhar is hiding in the covered boat in his back yard and calls Tommy and Superintendent William Evans.

In addition, cameo appearances include: David Ortiz walking from the dressing room to the field at Fenway Park, before switching to archival footage of him speaking to the crowd the day after Dzhokhar Tsarnaev was captured; Dun Meng inside a pizza restaurant in a scene where actor Yang – sitting at an adjacent table – is portraying him; David Henneberry, who found Dzhokhar Tsarnaev hiding in his boat, as an unnamed citizen standing on a front porch, briefly talking with Wahlberg's character.

[13] Its final version, not focused specifically on Davis, was written by Peter Berg, Matt Cook, and Joshua Zetumer; Mark Wahlberg plays police officer Sgt.

[14] Wahlberg produced the film along with Scott Stuber, Dylan Clark, Stephen Levinson, Michael Radutzky, Hutch Parker and Dorothy Aufiero.

[24] On April 6, 2016, Rachel Brosnahan and Christopher O'Shea joined the film to play newlyweds Jessica Kensky and Patrick Downes, who were at the finish line and seriously injured.

[26] On May 5, 2016, Melissa Benoist was cast as Katherine Russell, the widow of Tamerlan Tsarnaev, with Khandi Alexander set to play law enforcement interrogator Veronica, and Jake Picking as MIT Police Officer Sean Collier, who was killed 79 hours after the bombing.

[33] Filming was arranged on Laurel Street in Watertown to recreate the shootout that took place there between police and the Tsarnaev brothers; but after objections by residents, town officials denied permission for the location.

The Massachusetts Institute of Technology, where the Tsarnaev brothers killed MIT Police Officer Sean Collier, allowed the film production to shoot "entirely peaceful scenes" on the campus for three days in June.

[45][46] Academy Award-winning composers and Nine Inch Nails members Trent Reznor and Atticus Ross were hired to write the musical score for the film.

The website's critical consensus reads, "Patriots Day offers a stirring, solidly crafted tribute to the heroes of a real-life American tragedy without straying into exploitative action thriller territory.

[53] Peter Debruge of Variety wrote: "It's genuinely exciting megaplex entertainment, informed by extensive research, featuring bona fide movie stars, and staged with equal degrees of professionalism and respect.

"[54] Wendy Ide of The Observer gave it 4/5 stars, writing, "As a police procedural, this is first-rate: unflinching, briskly paced film-making that pieces together the fast-moving investigation in a wholly satisfying manner.

"[57] The Atlantic's David Sims was more critical, writing, "The Boston PD's efforts to capture the Tsarnaev brothers is justly depicted as heroic, but it's the crazed decision-making, the random chains of events, and the empty, angry posturing that stick out as most worthy of analysis.

Yet Berg is a filmmaker of some artistic ambition, and there are occasional intentionally discordant notes – including a menacing electronic score by Trent Reznor and Atticus Ross.