Three days before the film's release, 87Eleven Entertainment, known for the popular 'John Wick' series starring Keanu Reeves, announced that they had purchased the rights to remake the movie in Hollywood.
Almost 90% of the film is set in a train.
According to Wikipedia (and sources linked there), this film is based on the real life events surrounding Bishnu Shrestha. Single-handed, he confronted 30-40 bandits on the Maurya Express in 2010. A retired Gurkha apparently never really retires - he stepped in to stop the rape of an 18 year-old woman near him, continuing to fight with his khukuri knife (Gurkha standard issue) until overpowered. Though severely wounded, he killed 3 and wounded 8 robbers. He is quoted as saying: "Fighting the enemy in battle is my duty as a soldier. Taking on the thugs on the train was my duty as a human being." It is reported that he was unretired by the Indian military to be awarded medals for valor and promoted.
The movie had a casting of complete newcomers (Ashish Vidyarthi and Harsh Chayya were the only experienced actors).
The film was a surprise hit.