No, I understand you and you're right. Even though it was CCTV, it's been transferred to video at probably either 60 frames a second or 24 frames a second, so there's a lot of loss like you say.
I don't think we'll ever know by looking at video of the blast. Another video of a police body-cam taken less than a minute before the explosion reveals that there was nothing on the other side of the street that could have caused the explosion:
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