probably just one of those good old boys (with a gun)...
...
The shooting started around 2:30 p.m. after the man set off an alarm while going through a metal detector and "drew what appeared to be a weapon and pointed it at a police officer, Capitol Police Chief Matthew Verderosa said.
The gunman was immediately shot by a police officer, Verderosa said. He is undergoing surgery and his condition was not known, the chief added.
No charges had yet been filed, Verderosa said.
"We believe this is the act of a single person who has frequented the grounds of the Capitol before," Verderosa said.
Law-enforcement sources identified the suspect as 66-year-old Larry Russell Dawson, from Antioch, Tenn.
more:
http://www.nbcnews.com/news/us-news/u-s-capitol-building-lockdown-n546776?cid=eml_nbn_20160328