If you compare the backpack in the two photos, the one on the bike looks much more boxy with the contents, top and bottom. Yet he may have even be carrying an ebike battery with him during the shooting, so if that is the case, it should be fuller before not after.
I'm wondering if he bought two identical backpacks, one clean one (no DNA) to leave in the park to be found, and the other dumped in a dumpster or trash cart which police wouldn't be looking for.
Did he change coats too in the bike photo? Is it a longer coat? His arm looks well padded to me. The taxi photo coat looks like a different coat to the one in the shooting.
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New photos show masked suspect gunning down UnitedHealthcare CEO and fleeing on bike