I wondered about that too. One possibility that's still consistent with the details reported in the article is that the killer and his friends might have just been bumming around, when to the surprise of the friends, the killer said something like, "hey, come and watch this", and then pulled out the gun and began the robbery. They could have been too stunned or scared to either leave or try to subdue their friend, and then it was quickly over.
In a case like that, I probably wouldn't consider the friends criminally at fault.
Not to say that's what happened, just saying that there are scenarios where the friends wouldn't have actually been co-conspirators in armed robbery or murder.
On the other hand, if they *were* willing participants in an armed robbery, hang them high, even if they were surprised by the shooting itself.
There was something about them being involved in an earlier attempt so I don't think they were innocents in the wrong place. Perhaps the authorities cut them a deal for coming forward or talking. I hope this isn't the case. When someone dies, they should all hang