The Miami Herald has a more complete timeline which includes the movements of Cruz as well as Peterson and other responders.  The story is behind a pay wall.  Here's a few relevant items:

At 2:27 p.m., six minutes after Cruz went into Building 12, the shooting stopped. Cruz ditched his AR-15 in the third-floor stairwell and left.

Five seconds later, Peterson radioed for officers to “stay at least 500 feet away at this point.” A dispatcher repeated, “Stay away from 12 and 1300 building.”

Coral Springs officer Tim Burton had just arrived at Douglas High. At 2:28 p.m., he radioed out the first description of Cruz: “White male with ROTC Uniform Burgundy Shirt” — exactly what the shooter was wearing when he was arrested later. How Burton obtained the information was unclear from the timeline.

MY COMMENTS:
No mention of body armor in the stairwell.  No problem with radios - the timeline contains a ton of radio traffic.  Most interesting is that 1 minute after Cruz left the building, a responding officer from a different police agency had a description of him?  Who told "Tim Burton" these things?

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