I’m not a lawyer, but there is simply no way, as you said, that they can prove a murder charge unless they are sitting on significantly more evidence. Also, as you alluded to, he was held and questioned by the police and not charged. How could a second-degree murder charge possibly follow that? No legitimate charge could, that’s for sure.
I’m not sure what to make of it. It might be grandstanding. It might be a rabid and overzealous prosecutor (Mike Nifong would have company in that case). It could be something else entirely. This charge is absurd on its face, so there’s got to be something else going on here.
I am thinking that if there was no charge there would have been riots in the streets and it would have gotten really ugly. If she had charged him with something less then 2nd degree a jury might have found him guilty of that. But she knows he is not guilty so she charges him with something high enough that she is pretty sure a jury would never find him not guilty of.