an africanized be is a honeybee but it is a different subspecies than the typical European honeybee normally found in the US. They are the result of an attempt to breed a hybrid of Euro and African honeybees in Brazil. Some of them escaped in 1957 and have ever since been moving northward. They eventually reached the southern US and are now starting to spread across the southwest US.
as I said before, most people cannot distinguish the difference between the 2 species. It generally takes a trained person in a lab to determine if a honeybee is of the africanized species or one of the many Euro species already in the US.
The biggest problem with the Africanized bees is that they are hyper-aggressive. They are no more venomous than a Euro B but they are much more protective of their hives. They will attack with little or no provocation and are relentless in their aggressiveness. I had read that one person was followed and attacked for over 1/4 mile. The reason they are termed "killer bees" is the fact that they do attack so much more aggressively. While their venom is no more potent than a euro B, the sheer quantity of stings causes people with mild reactions to react much greater, generally causing anaphylaxis, and sometimes death.
If you and or your family are allergic to bee stings, I would hope you each carry an epi-pen http://www.epipen.com/
Epinephrine is the treatment for anaphylaxis and a person with a severe reaction can die quite quickly. Quick access to epinephrine is the only thing that can save them sometimes. The Epipen is a self injection of epinephrine.
If your bees were africanized bees, they should be destroyed. Not only are they hyper aggressive, they are less productive than the established bees in the US. They will also take over an established Euro B hive converting it to an africanized hive.