When something is moving pre-open (or after-hours) and I don't know why, I turn to StockTwits. If I had a Bloomberg Terminal, I'd look there first, but I'm on a $9.99 a month data feed, not an $1,800 a month one. Twitter itself is too full of ticker symbol spam to be of any use, and no "free" news source is quick enough to report anything.
Here's the timestamp for the 8-K: Accepted 2016-04-12 08:00:50. There are a lot of opportunities if you're paying attention and can act fast.