10/16/2012 12:50 AM PDT

LAPD on 'Swatting' Pranks -- Someone's Gonna Die


The LAPD is gravely concerned ... someone will DIE if the rash of celebrity "swatting" pranks continues ... TMZ has learned. 

You'll recall Miley CyrusAshton Kutcher, and Justin Bieber have all been targeted by "swatting" pranks -- where someone calls 911 to report what they say is a deadly shooting, just for the thrill of seeing the SWAT team respond.

One law enforcement source deeply involved in the investigation warns ... if the pranks continue, it's only a matter of time before an innocent person is mistaken for a phantom shooter and gets shot to death.

Cops are alarmed at the rash of swatting incidents and fear they will escalate even more. They also say it's inevitable that someone waiting for emergency help may die while cops and EMTs are off responding to swatting calls.

But there's good news -- We're told the LAPD has several promising leads ... including electronic footprints left by the people making the prank calls. And in the case of Ashton Kutcher, we're told cops believe the people behind his swatting incident were scoping out his house, and nearby homeowners may be providing some hot leads.