Secret Video
In Chapter 7 continued of Part 1, after you kill Kaufman and his henchmen at the end of the level, go back into the vacant apartment you went through to reach the lobby where you fought Kaufman. In the apartment, you should find a home-theatre system. Turn on the flat screen TV. You will see a short video

Unlock Modes
Finish the game on Detective Mode to unlock Hard-Boiled Mode, New York Minute Mode, Dead Man Walking Mode, and the Jump to Chapter option. Finish the game on Hard-Boiled Mode to unlock Dead on Arrival Mode.

DOA Special Ending
Successfully complete the game in Dead On Arrival mode to view a special ending