I used to say, and still do out of habit, that I had to shoot an "attacking" rattler 'cuz my department had a very strick shooting policy, and that was my BS way of getting around it.

In southern CA, western AZ, the "Mojave Green" Rattlesnake is reported to be very aggressive. It is also the worst to be bitten by, its venom attacks both the blood and nervous system.

In Central/South America the Fer-de-lance is agressive and has very nasty venom also. It has a very high mortality rate in some areas. I came inches away from stepping on one once in Panama, I still shiver at the thought...