A few U.S Senators joined their House colleagues:

[Representative Emanuel Cleaver (D) (left) standing and speaking at the podium]

Cory Booker‏@CoryBooker
John Lewis @repjohnlewis and other members sitting in on the house floor for a vote on gun safety. #holdthefloor
[….] 1:14 PM – 22 Jun 2016

The republicans will be all atwitter about proper decorum.