Startling new footage of the Los Angeles news helicopter crash that killed three people shows the final seconds before the craft's deadly impact ... and the blades of the airship appear to have been stalled.

The security footage -- taken from a nearby business -- was shared by Los Angeles Aerial Photography on social media and it shows the helicopter's descent in slow motion.

It looks like the blades are stalled ... and the the National Transportation Safety Board is investigating the cause of the crash.

The crash killed the pilot George Marciniw, the reporter Eliana Moreno, and a pedestrian named Edy Gutierrez Mejia.

We reported earlier ... NTSB Investigator-in-Charge Fabian Salazar said their investigation into the deadly incident is just ramping up and that a report on the crash would only be ready in at least 30 days.

However, that timeline could go up to 18 months.

Salazar also brought up how video -- like the one above -- would be instrumental for the NTSB lab in determining what went wrong.

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