The film Patriots Day is fundamentally based on a true story. It is a historical docudrama that chronicles the events surrounding the 2013 Boston Marathon bombing and the subsequent city-wide manhunt for the perpetrators. The film aims to provide a fact-based, chronological account of the tragedy and the law enforcement response, drawing heavily from official records, news reports, and personal accounts of those involved. The narrative structure adheres closely to the real timeline of events, beginning with the bombing on April 15, 2013, and concluding with the capture of the second suspect four days later. Many of the characters are direct portrayals of real people, including Boston Police Commissioner Ed Davis (John Goodman), FBI Special Agent in Charge Richard DesLauriers (Kevin Bacon), and Watertown Police Sergeant Jeffrey Pugliese (J.K. Simmons). The film also incorporates the true stories of victims, survivors, and key civilians like Dun Meng, the carjacking victim who escaped and alerted police. However, the central protagonist, Police Sergeant Tommy Saunders (Mark Wahlberg), is a fictional composite character. He was created to serve as a narrative guide, embodying the experiences and perspectives of multiple Boston police officers who were on the ground during the crisis. ...