AS police hunt gunmen in California, Americans are being reminded about the best ways to survive an 'active shooter' in a graphic video released by authorities.
The Los Angeles Country Sheriff's Department has retweeted the video this morning after the death of 14 people in San Bernardino.
The video, which includes dramatisation of shooting scenarios at offices and a mall, urges those caught up in a terrorist situation to keep a low profile and use cover to stop bullets.
It also urges people to get out using any means possible, including emergency exits, back rooms and windows.
It warns against people trying to take on an attacker, especially if they are heavily armed, but says the use of an improvised weapon should be considered as a last resort.
The video was produced in March and points out that active shooter events in the US with four or more deaths have occurred every 2.9 months.
It says the grim reality is that police will not arrive on the scene of such shootings for at least several minutes, so it is up to those at the scene to survive any way they can.
The use of a secure room, with all entries barricaded is one suggestion.
It also recommends staying away from all windows.
Each year, there are 20 mass shootings in the US, sparking calls for greater gun controls, like those used in Australia after the Port Arthur massacre.
VIDEO: WARNING GRAPHIC CONTENT