Utter rubbish; the airport was PACKED with people right inside the gate and on the airplane, no less than 120 in the plane alone!
That goes for the rest of your self-serving post, too.
Source? There has been no media reports of that...if so there should be plenty of witnesses to collaborate the air marshal's version of what transpired off the plane. So far I've seen only one media report of one woman inside the gate who heard the shooting, but didn't see it. She did not mention any of the dialog the air marshals reported, but perhaps others will.
As for "self-serving," the air marshals' version serves their interests; and one important part, that Alpizar ran up and down the aisle yelling, "I have a bomb in my bag," appears from the reports of independent witnesses, not to be true.