What are smoke grenades? Why New York City subway shooting is concerning

A masked gunman set off two smoke grenades and opened fire on common people in a New York subway car on Tuesday (April 12). He injured several people in the morning rush hour in the city.

No fatalities have been reported so far. Authorities informed that ten people were hit directly by gunfire.

The smoke grenades are signalling devices, target or landing zone marking devices used by the military. They are normally non-lethal, but incorrect use may cause death.