the amount of stress the media are putting on 'this is not a terrorist attack' would suggest the killer isn't Caucasian; if he/she was and the victim was non-white they'd be desperately looking for a link to it being a racist attack
They've said the killer is black. Don't know about the victim. I think they're stressing that it's not a terrorist attack to avoid undue alarm because in the current climate that's the first thing people will think of. On the face of it I imagine it's a domestic issue - but I might be wrong.