Same as I was thinking.
What I don't know is if the marchers he hit were in between side streets.
I saw footage where he was speeding, but in an open lane. Then he gets to a point where the whole width of the road is being used, and he hits marchers, Finally, there is footage where he goes past a road block and shots are fired.
That roadblock could have been a side street that was blocked because of the parade, not unusual, and it may have been the first side street he came to.
Have to see a map of the fatalities to see if they occurred on a stretch with no side streets before a chase gone bad theory can be eliminated.