From the Inquirer. This largely matches what I saw.
Anyone who wants to take a close look, I would recommend screen capturing the video and slowing it down. You can pretty clearly see the following action happen:
On the video, the two groups walk toward the cameras mounted outside the Fox29 studios at Fourth Street and Market: Ung and friends, then DiDonato and his friends about 10 feet behind. Kelly, recognizable in a white cap worn backward, darts into Market and walks ahead to flank the trio.
Ung kicks at Kelly, backs up, and holds up a gun. Suddenly, DiDonato moves forward and appears to lunge at Ung.
Twice Kelly rushes to the sidewalk at Ung. The first time he is pushed away by the woman. The second time, he gets through.
And that’s the point where Ung starts firing. It looks as if DiDonato fell onto Ung, which can explain why Ung kept firing. It would be difficult to tell the difference between someone falling on you, and continuing to attack you.