"Lock the doors"

Those was the words used by Flight Director Leroy Cain when it was determined that the Columbia was lost.

Ars Technica has an excellent article on the sequence of events.

HERE

It should also be noted that the foam composition had changed. The environmentalists (and the EPA) had caused NASA to change the foaming agent and the foam composition to one that was less toxic and more environmentally friendly....this made the foam much more brittle. So the foam strikes happened because the EPA and a few environmentalist were worried about a bit of Ozone Depleting Chemicals and a few pounds of not so terribly toxic material that might vaporize....a few POUNDS....

7 people died to save the ozone...