Perhaps it was an accidental launch. It might not even be the JL-3.
there is no such thing as an accidental launch of an SLBM. even assuming that there are absolutely 0 permissive action links and any random sailor can launch by pressing a single button, you must be at launch depth to even attempt to launch and the probability of being at launch depth, far shallower than operating depth, while an accident occurs simultaneously, is vanishingly small.
now my question is, why do you suggest accidental launch? what are your motivations for suggesting this when this sort of event has never occurred in all of history and is something that is guarded against by design in every single strategic weapons system since the 1950's? we all know the answer to that.