Civil engineers need to go in for a though inspection and lab testing. I don't think I am the only one to question the collapse into it's own footprint strange. Rebar pulled straight out of the concrete and it has no rust, or maybe not visible on camera. Majority of concrete is small chunks not large except the floors. You wouldn't expect the upper wall pillars to kick in which would then cause the upper floors of the building to topple not pancake.