They could term it that, but with the lack of information released at this point I'm not going to make that assumption. Homicidal violence does not mean that there was a beating. A gun, knife, or car all could have been used and it would still fall under that definition. It's a very vague COD to use and I'm guessing LE did that on purpose. And I think you are overestimating the evidence that is left behind in a car-hitting-person accident. There could maybe be glass fragments from a headlight or something like that, but something like that wouldn't be super noticeable lying on the street, and could easily be swept away. And if by "evidence of an accident" you mean blood well I would say that is not always the case. If he was knocked down in front of the car and then run over by it there can be fatal internal injuries with very little external blood. (sorry for the graphic description, but it's true.)
Again, I am not sayin I think this is what happened, but it fits with a lot of what we do know. And I also have trouble believing that any of his friends had anything to do with it. Just doesn't add up. If anyone thinks an 18-20 year old college kid could mastermind their friend's murder and not make a bunch of mistakes along the way then you need to go spend some time with some 18-20 year olds.