"The US Capitol building was placed on lockdown on Monday after police opened fire on a man who brandished a gun on the premises.

The order to shelter in place came after gunshots rang out in the vistors centre of the building, which houses both the senate and house of representatives."

https://www.telegraph.co.uk/news/2016/03/28/us-capitol-on-lockdown-after-shooting-at-visitors-centre/