Who really killed Mr Brown in Reservoir Dogs?

(Spoiler Ahead)

In the movie Reservoir Dogs Mr Brown (played by Quentin Tarantino) is found dead after Mr White (Harvey Keitel) shoots down the cops. However before the brief shoot out he was talking to Mr Orange (Tim Roth) and complaining about blindness and blood in his eyes.

Although Brown was already injured, however his sudden death due to those injury looks a little vague to me. It is fairly possible that Orange would have shot Brown while White was shooting at the cops. Is there any pointers in the movie explaining his death in the movie?

• Next Word for changing or shortening or abbreviating a given name
• Previous science fiction - Movie in which time is money