The phone is more likely a smartphone, and not a flip phone. They were remarking on the way that the individual stylistically flips the phone in his hands when he pulls it out. They are hoping someone in the area knows someone who pulls their phone out like that and reports them.
I live in the neighborhood on the other side of 275. My brother lives in a house just off 15th street and Giddens and heard the shots ring out during the first shooting.
A few opinions--someone of which have been mentioned before--I believe it is a male based on the posture and statistics. There is definitely something unique about the way they pull their phone out. In the latest video of them running, you can see the individual favoring their left pant leg with their left arm, which is most likely where the gun is. The phone was pulled from the right pocket, which further supports my previous speculation. The clothing is absolutely too warm to be wearing in the weather these shootings were committed in. The way this individual is running doesn't appear to be fearful, and looks as if they're trying to run away, but also not look like they are.
This is a very dense neighborhood with lots of side streets, alleyways, etc. Lots of bushes and landscaping, giant oak trees, etc to hide behind. Also, many cars parked on the street.