Anton Petrov has pretty decent coverage of this on his YouTube channel[1].
This type of supernova has been theorized, although to my knowledge not previously observed (due to the mechanics, about 50% of the energy is radiated as visible light, which is why they're so exceptionally bright).
We do have a star near us that is theorized to have undergone a pulsational pair instability supernova in the 19th century: Eta Carinae.