Jake Gyllenhaal witnessed a murder while preparing with the LAPD for a film!
End of Watch was a 2012 film shot documentary style about LAPD partners who make a few good busts and the Mexican drug cartel orders their deaths. The film was loosely based on real life LAPD partners, Charles Wunder and Jamie McBride, from the 1990s.
As part of their training, Jake Gyllenhaal and Michael Peña spent five months doing 12-hour ride-alongs with on-duty LAPD officers. During Gyllenhaal's first ride-along, he witnessed a murder. Gyllenhaal and Pena improvised most of the banter between them in the film.
In law enforcement, "end of watch" has two meanings; it commonly refers to time to go off duty at the end of shift. Also, if an officer is killed in the line of duty, the date of his death is referred to as his end of watch.