Potus walked in to Hall of Heroes at 4:30. He walked on stage to join Vpotus and Sec. Mattis.
Vpotus thanked all for being here for the swearing in of Mattis, noted the history of the room we are in, and detailed the defense secretary's extensive military history.
Vpotus then administered the ceremonial oath.
Potus looked on. The room erupted in applause after oath finished.
Mattis gave brief remarks, thanking Potus for having "confidence" in his ability to lead the Pentagon.
"Total confidence," Potus said.
"That's total confidence, believe me," he said, taking the mic.
Reading remarks, Potus praised the military as "Backbone of country" and "spirit of this nation."
(More from remarks in next report.)
Potus signed two executive actions, one on rebuilding the military and another on "extreme vetting," according to press secretary Sean Spicer.
Pool estimates that there are seats for 60-70 here, filled with military and civilian leadership of the Pentagon.
Pool spotted NSA director Adm. Mike Rodgers, fmr SecDef William Cohan, as well as aides Kellyanne Conway, Hope Hicks, Sean Spicer, Michael Flynn, Steve Bannon, KT McFarland, Reince Priebus and Stephen Miller.
Conway was wearing the same jacket she wore at Potus' Inauguration last week.
Just outside the Hall of Heroes pool spotted a big Winston Churchill bust, which, pooler is informed, has been here a while.
Pool exited room at 4:43 and headed for vans.
At 4:47, we took a brief detour to see Potus shaking hands with a line of members of the US military.