Suddenly an ambulance approached his family's house.
Mirwais Yasini, a member of parliament who was nearby when the explosion occurred, said an ambulance approached the checkpoint and blew up.
Soon after the explosion, an ambulance approached the site, but medical responders were held back by carabineros — Chile's national police force — and were unable to provide assistance as officials scanned the area for other threats, witnesses and media outlets said.
Soon, the officer called in backup: the street was blocked off by two squad cars, and ambulances approached.
Police doesn't let ambulance approach #rbnews #18ogr twitter.com/Stathisgr/stat… October 18 , 201212.32pm BST According to local reports, there were riot police on every Athens street corner, with around 4,000 officers deployed.
An expert in ultrasonics and materials evaluation, Wooh proposes a system that would rely on the Doppler effect-the shift in the frequency of sound waves that occurs as a moving object, such as a whistling train or wailing ambulance, approaches and then recedes from a stationary object.
These flash in order to attract the attention of other road users as the ambulance approaches, or to provide warning to motorists approaching a stopped ambulance in a dangerous position on the road.
When you're on the street and an ambulance approaches, then races past, the pitch of the siren will increase as the ambulance gets closer, then drops sharply as it speeds away from you.
Another demonstration shows how drivers in standard cars can be given information, such as whether cars in traffic ahead are braking sharply, or if an ambulance is approaching.
