Initial reports are never right, but today was really strange. Who are these guys?
1) It seems clear that this was a semi-professional team of guys who knew how to work together, and who had either the capacity to make pipe bombs or connections who did. They carried out their plan and managed to exfil successfully before police could arrive. Yet hours later, they're still driving around in the same car, in the same kit, a mile and a half away?
2) The target doesn't make any obvious sense as a terrorist target, except that it was a soft target with lots of people.
It's like you had a team of guys who meticulously planned out how they'd carry out a major attack, but never got further in their planning than how they'd drive away from the scene within a given response time, leaving IEDs to cover their tracks. There was apparently no "then what?" considered. There were major freeways they could have taken, and if you've got three guys you surely have access to more than one car. They could have dumped the SUV and their kit, piled into a white sedan, and been in another state by the time the police caught up to the first vehicle.
Wannabe martyrs? One of whom lost his nerve and fled on foot when the final firefight arrived? But then why bother with the exfil? You could have stayed and killed a few more people, and become martyrs where you were. The police were coming.
It's like they had everything mapped out until a minute after they drove away, and then suddenly realized they had no idea what came next (and no imagination between them that would let them plan up something better than 'drive around the neighborhood in the getaway car').
The one thing that might make sense is if they had been trained by professionals who considered them disposable. They were taught how to do the part they did right, and then... what now?
Or maybe they're just yahoos who thought this out carefully on their own, and weren't bright enough to think beyond it.
Otherwise, conflicting details in all the reports make it hard to know what to think so far.