It happens everywhere. In US, guns make it easier. In Poland (and Russia) vodka makes it quicker to happen and is almost always involved. In fact, it's so universal that I can tell a lot about Hicks without even meeting him (in fact, enough not to ever want to meet him). I can keep away from this kind of scum, so I do, but this is not always that easy. They're usually lower class (if one of them somehow gets higher than that, you get the worst kind of
noveau riche), but so are many nice people who don't have an option of "just move out of this crappy district".
Remember the guy who shot someone in the cinema that was on here a few months ago? That was less than this even if it was just a single incident, and it was something that was ongoing, allowing rage to build up.
This is likely exactly the same reaction. Yes, three people because of a parking space. I've seen local news reported on people did worse (or tried to) for equally petty reasons. He likely was in the wrong, or otherwise unable to have this dispute resolved in his favor. It likely dragged on for quite long, too. This is something akin to beating up one's husband because he leaves the toilet seat up. Weak, unintelligent people often resort to violence when they have a problem and can't think of a way to solve it (not only against humans, this kind of reaction can also manifest as swearing and hitting a defective appliance that fails to work). This also goes hand in hand with acting on emotions instead of thinking.
He could hate Muslims, Blacks, immigrants, everyone different from him. He probably does, since lack of tolerance common to this kind of people. But it's unlikely this was a hate crime, though it might have contributed to his frustration and accelerated it a bit. He hated those people in general, and in a more "personal" way than blanket hate for entire ethnic groups. Also, it's quite likely that this dispute contributed to his hatred of Muslims as well - it's common for anger at specific members of a group to be transferred to the group in general (TBH, many people are guilty of that one, not only uneducated louts).