I posted earlier - if you want a fuller account, courtesy of TSOs who posted here regularly, you'll have to search the forum (and it can be a pain, sorry).

A frequent TSO poster (allegedly a trainer) told us that TSA recognizes and defends against the possibility of multiple bad actors departing from different airports, meeting at a common connection airport, and assembling the stuff they have brought into something nasty.

For instance, that was used to explain why a shell casing gets confiscated. What can you do with a shell casing? Well, you can meet friends in the sterile area who have arrived on other flights, bringing more necessary bits. Put it all together and you have a problem.

So...according to that teaching, this guy may have had contraband on him that he planned to give to a partner he was meeting on arrival or he may have been stashing it somewhere in the terminal so that someone else could retrieve it and wreak havoc.

A supervisor at T2 PHX told me that pax and their belongings are subject to search at anytime without warning and without a requirement to do it in the sight of the pax. Nothing to do with SSSS - this applies to all pax (but not TSOs or airport workers).

I can't find the link right now, but there was a particularly nasty situation where a smaller plane landed on the tarmac. It was boarded by TSA/DHS/FBI/? armed officers who told everyone on the plane to be quiet and put their hands on their heads (including little kids). Lots of threats - any movement, someone might get shot, etc.

It didn't matter that the plane had arrived safely and supposedly everyone on it had been screened and cleared by TSA. Everyone on the plane was suspect until they were cleared again.

You probably missed it when a TSA team went to a railway station (not a huge one). All arriving pax were diverted from going directly to their cars. They were forced to enter the station ('sterile area') and undergo a full bag and body check before being allowed to proceed. Please note: these were pax who had arrived at their final destination and they did not have to go through the sterile area to reach ground transportation. They were forced to go that way.