Mark Bomback is a screenwriter who works primarily in the action/adventure genre. One of his first projects was a re-write of the original script for "Constantine," an action-science fiction film directed by Francis Lawrence, adapted from a comic book. Not only were there accommodations made to the main character to make it a better fit for Keanu Reeves, but a lot of plot elements, locations, and aesthetic elements were changed as well for various production reasons. A few years later, Bomback wrote the final script for the fourth installment of the "Die Hard" action film series starring Bruce Willis, "Live Free or Die Hard." As with "Constantine," there were several changes to the original script, as well as each subsequent script. One of the main reasons for the numerous re-writes was an effort to be more sensitive, as the project was originally supposed to have been released around the time of the September 11, 2001, attacks, and the plot's central theme dealt with terrorism against the United States In 2009, Bomback worked on the final script for the remake of the Disney science fiction adventure film "Escape to Witch Mountain," called "Race to Witch Mountain," directed by Andy Fickman. After Dwayne Johnson (aka The Rock) was cast in the lead role, Bomback was asked to modify the original script significantly, adding more dark elements to the plot and overall mood than were in the original film. In 2010, Bomback wrote the script for "Unstoppable," an action/adventure thriller about a runaway train, for director Tony Scott, who is famous for the adaptation of another train-based thriller, "The Taking of Pelham 1 2 3."