How do I read the kill icons in League of Legends?

The new League of Legends patch (1.42.34) added in a "Kill Stream" (as well as a lot of other neat UI cleanups. It looks very pretty now, but I digress...) in addition to the announcements of "So and so has slain such and such" etc.

There appear to be at least three separate kill icons - A blue fireball, a yellow sword, pointing downwards, and a red sword, pointed right.

What do each of these kill icons represent?

Solution 1:

[W]e went with kill, streak, streak ended.

—LoL UI Designer

And from their published screenshots here and here:

• Single Yellow Sword: Kill
  

• Multiple Blue Swords: Kill Streak
  

• Downward Sword: Breaking someone's kill streak
  

The background is if it was a kill for your team (green) or theirs (red)