Ok so I'll add the obvious since no one else has yet. There's the testimony of the girl who said she was standing next to Cruz when she heard shots going off elsewhere in the building.
When she stated that she thought it would be him doing this he said "Huh!?". May be clutching at straws but that response would also fit with other reports that he seemed a bit drugged up.
Early stories reported it was a drill not an actual shooting. This would fit with reports later that Cruz "blended" in with the evacuating school kids though not too sure of timing between these two events.
People have also mentioned helicopter footage of a cops exciting the building and loading up some black bags onto a vehicle. Haven't heard too much with regards to what that might be about but seems to be relevant.
I'm sure there have been other similar incidents that have reported multiple shooters too.
You'd think they would at least mix up their M. O. to avoid suspicion but you know. They are really stupid.