It’s probably a felony murder charge. Punks 1 & 2 approach the driver who has a CCW permit and assault him in a way that causes him to reasonably believe he’s at risk of death or great bodily harm (such an assault can be verbal, as well as physical, if it contains racial insults and physical threats) and the assault’s target fires in self defense, wounding punk 1 and killing punk 2. Punk 1 probably committed a felony in initiating the assault; thus, when punk 2 was killed in the course of that felony, punk 1 became liable for murder under the felony murder rule.
That's exactly what it is. Felony murder charges are quite common here in Florida, though the doctrine has been abolished in a number of other states. If someone -- anyone -- is murdered during the commission of a felony in which you are an accomplice, you get hit with a murder charge. You see perps getting socked with this all the time where their partner-in-crime has been killed.
Also, anybody who thinks the driver with the CCW should have just warned these two off with a gun is nuts. I've read a number of the local news reports down here on this case. The guy in jail is 6'3" and close to 300 lbs, and was known as a total hothead. I don't blame the driver for not just pulling his piece and politely asking him to go away. The law doesn't require that here in Florida. See this statute for details.