I speculated that myself early on, but given what's emerging about his fixation and rage at LDS going back over a decade, I think, like the death of the prophet, it's going to turn out to be a coincidence or just one more thing rather than a true catalyst.
He hated LDS, he thought they were the Antichrist and trying to take over the world for no real reason besides a bad breakup he had that he has never let go of despite having a marriage and a child since then with another woman. Who knows why he decided that Sunday was the day, but from everything that's being said, he was like a train on a track headed that way for a long, long time.
MOO