Big question is why? A 90 day extension of the time the warrants and the findings of the warrants are sealed.
A very good question. One I asked and one some of the media asked. There wasn't a good answer. It's not normal. Usually, I read, it's anywhere from 24 to 168 hours, to give LEOs time to follow up leads and arrest accomplices. It was fairly obvious, from the beginning this was a lone wolf, not part of some larger conspiracy or terrorist act. There will never be a trial.
Also strange was, even though the school was an obvious crime scene and it's beyond me why anyone would need a search warrant for the school, they got one. Was it to shield the evidence? Otherwise all findings would have been available within a week.
Let's take a look from a different angle. What if LEOs and prosecutors got the 90 day gag-order because they believed something was going on beyond the obvious? Did they believe some conspiracy theory? Maybe they thought some VIP was involved somehow?