Ah, it's a private garage, everyone knowns each other in this building, and the place has only one entrance so it's impossible for someone to enter there without opening the door that was right behind me, car entrance warns an incoming vehicle with lights and sounds in case someone is behind the garage door. And the apartment's attendant knew i was recording this. The place is also somewhat soundproof, because there is an electric generator in a closed room, and doors were sealed to avoid the engine to be heard.
It's actually the safest place here to try out an airsoft.
I'm just saying, shooting in a place with a well echo is really fun and can be used to compensate the bass loss of recordings (like only the motor of the airsoft can be heard, while it goes bang in real life)