This two-out scenario was the result of a low pull followed by an AAD fire (CYPRES), and the skydiver reacted quickly by cutting away the main while it still had separation from the reserve. Here's what the jumper had to say about the incident:
"The jump was done at a DZ that I was visiting for the first time, I attended a standard DZ briefing. The elevation of the DZ is 2000 feet higher than my home DZ and jump run was 10,000 feet instead of 13,000 feet. The first jump of the day was from a helicopter with an exit altitude of 5000 feet. This jump went off flawless. However, something must’ve happened on that jump with my audible altimeter because on the jump in the [two-out] video the audible never made a sound. I found myself on a sit fly jump having lost altitude awareness because of no sound from the audible, and my “internal clock” hadn’t gone off because it didn’t register that I have less free fall time given the lower jump run altitude of the DZ. At 2200 feet, I realized where I was and immediately transitioned from a sit to belly while deploying my main. By that point I was already too low and didn't have line extension until below 1,000 feet, which resulted in a Cypres fire and cutting away my main.
Things to consider: