Under Florida law, anyone who commits a felony such as armed robbery resulting in a death can be held accountable for the capital offense.Sucks to be you, Mr. Criminal. I think you actually got off easy. (12 years in prison.) Florida is death penalty state, and while they aren't as serious as Texas, they aren't New York either.
This is the culmination of a 2007 case where 2 guys tried to rob a Subway Sandwich shop in Plantation, Florida. But they ran straight into a retired Marine, John Lovell. You can read about the original incident at this link. Suffice it to say that legal concealed carry works. (And actually I know the bad-guy got off easy; his accomplice in that failed robbery was killed at the scene.)