Whatever is said there, the rest seems to be rather clear: 1) he was pursuing Trayvon, and Trayvon had begun to run or move quickly--most likely because Zimmerman looked threatening (note that Trayvon's girlfriend indicated that Trayvon told her on his cell that some guy was following him so he was going to walk fast. 2) Zimmerman followed him despite being advised by the 911 operator not to do so; 3) Zimmerman knew the cops had been notified and were on their way, because he was told that directly, and, 4) Zimmerman also muttered that the "a-holes" always get away.
This man was aggressively pursuing Trayvon when there was no need for such an activity, and he was doing so while armed. From what I've read, he had aspired to be a police officer. Seems he was trying to play cop that day and Trayvon's death was the result.
What bugs me is that this guy most likely won't be convicted of anything, unless he makes incriminating statements, because, so far, no eyewitnesses have stepped forward.