This is so frustrating, because I get what you're saying and wish the legal system didn't work the way it does.
My thought is this: had he NOT been given medical attention, would he have died from being beaten with a hammer? It sounds like YES, considering he died even after treatment.
If that's the case, what excuse does someone have to beat another person with a hammer without the intent to kill them? This wasn't an argument in a workshop gone bad, these were two individuals who walked around with a weapon specifically to use against other people in targeted attacks.
And they didn't just try to kill this one guy, they targeted and attacked multiple people from the sound of it.