Surprisingly only the lead new martial arts so the director had all the actors train for 4 weeks on combat choreography.
This film was shot as a tribute to the Wachowski brothers in between the Matrix release and during the filming of Matrix II. Andy Wachowski was on set in Alameda California filming Matrix II when he was contacted and invited to the release. He mentioned that his brother was Australia filming an therefore they could not make the premiere.
The filming could only be done and night and on weekends so it took 3 months to complete using Friday, Saturday, and Sunday nights.
Over a 1000 blanks were used in the firing of the glocks and automatic weapons and the concussion of the auto weapons fired was so loud that it knocked out some of the lights in the hallway of the building where filming took place.