US Capitol is on lockdown due to an external security threat

The US Capitol is on lockdown due to an external security threat.

An announcement made over the PA system told everyone to stay indoors and away from windows..

CNN’s Lauren Fox reports seeing ambulances and a helicopter outside the building. One person was seen on a stretcher.

DC Fire spokesman Vito Maggiolo says they are responding to a reported shooting at the north barricade of the Capitol and there are indications they will be transporting patients.

This story is breaking and will be updated.