I don't know. They haven't gotten into the specifics of the parking dispute beyond what I already said. I'll post anything else I might come across.
And FYI, getting shot in parking disputes is waaaaaaaaaaaaaaaay more common than getting shot for being Muslim.
P.S....this dude is a liberal atheist. Liberal atheists are not known for religious murders. He used his social media to bash all religions equally. Including Christians. Atheists tend to do that. Atheists are generally hostile to all silly beliefs about the man in the sky.
You may note that I have not jumped on the Muslim angle as motivation. That is because the investigation does not conclusively state such. Likewise none of the articles that I saw make any reference to the victims parking in what is the shooter's officially assigned parking. So your comment that the victims were wrong and strong s without merit.