I mean this is the beginning of what seems like a massive, probably international effort, to figure out what happened and who's responsible. Russia is known to be involved in state sponsored cyber intrusions, so it's natural the initial speculation would gravitate in their direction; But it could very well be from within the US borders, or some other nation entirely. That's what the investigation(s) will try to figure out.

From now until that day, I will simply assume nothing.