<BBM for Focus>
The likely explanation for the big gash on MB's hand will likely be provided by forensics; prints, blood, skin/dna, etc...
Imo, and according to some witness accounts during the initial altercation, MB fought over officer Wilson's firearm and it discharged inside the police cruiser, it likely injured MB's hand when the slide then moved forward feeding the next cartridge from the magazine into the chamber.. jmo
http://www.inetres.com/gp/military/infantry/pistol/M9.html
The M9 is carried by crew-served weapon crewmen and by others who have a personal defense requirement, such as law enforcement personnel and aviators.
The 9mm pistol has a short recoil system utilizing a falling locking block.
Upon firing, the pressure developed by the combustion gases recoils the slide-barrel assembly. After a short run, the locking block will stop the rearward movement of the barrel and release the slide which will continue its rearward movement. The slide will then extract and eject the fired cartridge case,




the hammer and compress the recoil spring. The slide then moves forward feeding the next cartridge from the magazine into the chamber.