BMPCC made "Fire Alarm" sound til turned off. What gives?

While shooting behind the scenes footage all day at a commercial shoot my camera suddenly made a high pitched, very loud continuous tone. It sounded like a fire alarm going off. It wouldn't respond to any controls except turning the power off.

I had just recorded a sequence and hit the play button to review it. The tone didn't happen immediately (I was distracted by other activity on set for a few seconds.) Suddenly, the tone comes on full, louder than I've heard any playback out of the unit. (The speaker volume was set to 0% at the time.) The screen was on the first frame of the video I was trying to play back, but, was not playing. The tone continued for some time, probably over a minute or so (It wasn't until I moved about the room to find the source that someone figured out it was in my hand all the time.) I hit play, ff to no effect. Holding down the power button and powering off stopped it.

Upon powering back up everything worked find again. The clip loaded and played back as normal.

Luckily it happened between takes, but, it was unnerving to say the least. What would cause the camera to act in such a way?

Christopher Schiller

Going out on a limb here, did it sound anything like audio feedback?

Two things make me doubt it was feedback. One, it was not in record mode. Two, the speaker volume was set to 0% so there should have been no audio source to be feeding back into the mics. And It didn't have the ambient build feeling of feedback. It really did sound like an alarm sound. Single tone, very high pitched. And if it was feedback, why wouldn't hitting the play/rw/ff buttons have an effect? You'd think it would go into play or change to another clip or something. It seemed stuck.

I'm at a loss to explain it (and I thought I'd seen everything on a shoot.) Keep the guesses coming, though, cause I'd hate to ruin someone else's take if it goes off again.

Christopher Schiller