In a recent freak accident, a woman motorist was choked to death as she poured water into her radiator. Her scarf got entangled in the running engine fan and she was unable to extricate herself. Even though it seems unlikely, accidents like this do happen. In fact a similar accident happened here in Saudi Arabia with a motorist whose gutra got caught in the fan. Fortunately, the man was not killed, but he suffered severe cuts to his face.
To avoid this risk, do not add coolant to your car engine while it is running. Turn the engine off and allow it to cool completely before adding coolant. This will also avoid the risk of cracking the engine block by adding cold fluid to a hot engine.