Early warrant exercise is unusual. But I have seen it occur, essentially out of the goodness of the warrant holder's heart, in order to get money into the hands of the issuer, which, in the long run, may prove beneficial to the warrant (now stock) holders, too.

But it certainly is nothing new to sell shares short when you hold warrants that enable you to cover.

Are any of the warrants themselves publically traded? If not, or only a small portion of them are, then it may be that warrant holders would like to get some cash out soon. That could be what happened today; if so, hopefully will be a one day event, but watch carefully. So much emphasis has been placed on April 28, that those wanting to cash in some profits may be figuring these days leading up to April 28 are the ideal time to sell some shares without tanking the stock price.

Nothing new, especially in the Venture Exchange. Generally speaking, those who buy or are granted warrants or options, are a bit less emotional than retail investors.