CLEAN : Witness reports massive bang as helicopter

The transcript describes a sequence of events where the speaker is listening to the radio, waiting for a call, and then experiences a sudden impact. Initially thinking it was someone behind them, they soon observe objects falling from the sky. The situation escalates as they realize a helicopter is crashing nearby.

How did the narrator react to the situation described?

What event does the narrator refer to when mentioning the 'helicopter falling'?