do you have any data to support your theory that legalizing pot would eliminate these shootings?
It's a mixed bag as far as data is concerned. If you look up articles about Portugal, they decriminalized everything in 2001, they mostly focus on the decrease in drug use and drug related deaths. There isn't much info on violent crimes associated with drug distribution.
Articles on Colorado are mixed, it looks like overall crime is down, but due to the legality of grow operations there may be an increase in violent crime because gangs fight to move that product out of state. We'd need decrimilization at a national level to see real effects.
I'd say there is plenty of evidence of decreases in violent crime after alcohol prohibition ended, since it eliminated most of the need for the Mafia.
Is there any data that shows drug prohibition is effective at reducing drug use or violent crime?