 A mechannic was reported to be using a pneumatic hammer,  which, when echoing up the elvator shaft, could be misheard as gunfire by those unaccustomed to either sound.
<fluency>  A mechannic was reported to be using a pneumatic hammer,  which, when echoing up the elvator shaft, could be misheard as gunfire by those unaccustomed to either sound.
 A mechannic was reported to be using a pneumatic hammer, the sound of which, when echoing up the elvator shaft, could be misheard as gunfire by those unaccustomed to either sound.