He had the high ground with unimpeded field of fire. He had multiple high powered full auto rifles with high capacity magazines or belt-feeds. The crowd was mostly static and there was little to no concealment available. A majority of the crowd was probably drunk or stoned making them more vulnerable. Easy peasy.
Meh... we don't know what kind of weapons he had. Remember, we're talking about the MSM that sees a rifle and, based on its color, will assume it's "automatic" if it happens to be black.
To someone who didn't know better, a rate of fire like 1-2 rounds per second may seem like an automatic weapon, but c'mon, that's just pulling the trigger fast. If you've ever heard full auto, or even 3-round bursts, you'd know the difference. Trouble is, most people haven't, so the typical interview with "man on the street" would be something like "...I heard automatic gunfire..." and the press will just roll with it.
I'd say it's high odds (90%+) that we'll discover he just had a few standard semi-auto rifles and a bunch of standard capacity magazines. He probably wasn't even a very good shot... as morbid as it sounds, if you're shooting into a crowd of soft targets, you don't need to be good to hit something. I mean, I highly doubt he was picking out targets and methodically scoping them, tracking their movement. He was just blind firing "jihadi" style knowing full well he'd hit "something".
Cowardly and evil, to be sure. I mean, what kind of evil gets into you to just blindly shoot at people like that? I'll never understand it (and hope I never do). It's the mind of someone just saying "f*** it, I don't care who I kill, as long as I kill", and that just does not compute. I guess you have to believe in a holy moon rock for that to even border on sanity.