Did you move too quickly? They don't like that at *all*
I've always found that you need to move quite slowly around a Blood or it's paranoia will get the better of it and it will go in to defensive mode. Slow movement around it if it's out and
very slow movement when approaching and handling is the key to these things. They're not Ball Pythons, they'll defend themselves in a heartbeat.
People think Bloods are lazy, but they're not - they're insecure. Those that think they're lazy should try moving quickly around one and they'll likely get to see just how fast they can be when they feel threatened.
To see a Blood get totally airborne as it launches it's considerable mass at an aggressor is an impressive thing, but with very slow and deliberate movements and very gentle handling one gets to know the limits of their snake and once you understand how these things really work, you can earn their trust and start having a good experience with them, but it can be a slow process because you do have to move so slowly around them and they don't really appreciate much interaction. It's worth it if you can manage it.
These animals demand respect and if their keepers forget themselves around them, they
will likely issue a reminder, lol.