Alex Kennedy on Twitter now says it was supposed to be a SnapChat "prank" that no one would see, but Russell got "hacked"...
BS
That's a complete lie. Snapchat videos are a max of 10-15 seconds.
I bet he sent it to the wrong guy/gal. Then they sold it.
If you're joking, I ^^ this post

If you're not joking, that is pretty much impossible. Speaking as a person that uses Snapchat, the whole concept is sending a max 10-second flash of a picture or a max 10-sec video to someone that then "disappears" after they view it once for said duration. There is no way to save the videos without others apps, and even then, the recipient needs to use the "saver" app before they view the picture on the regular app, which makes the "sent to the wrong person" possibility improbable, as an unintended recipient would have opened the video without any expectation of tabloid-able news. Also, Snapchat intentionally lowers photo/video quality compared to regular phone cameras, making the picture and audio quality of the Russell video unlikely. Combine that with the length and continuity of the video (it takes awhile to choose recipients and send snaps, making a longer-than-10-second, continuous video impossible), and I can't see how Snapchat was involved in this at all. It just seems like an excuse that will be easily dismissed by the public (because the 85% of the population that doesn't use Snapchat is so used to hearing about and dismissing youthful escapades that were failitated by the app; basically, it becomes a "well he thought it would go away and it's an accident" thing rather than a "snitch" thing for most of the general public).
EDIT: Technically, the videos are still saved on some internal memory on the device and in Snapchat's database, making them recoverable with the right tools/expertise. However, as I mentioned above, the continuity, quality, and length of the video make me think that even that extreme case is unlikely.