I understand what the Punisher symbol stands for. But most people like it because they think it looks cool or whatever and doesn't necessarily mean they believe in vigilante justice or think it's some sort of commentary on anything. Most people like the Punsher because they like the character and can identify with his frustrations and struggles with his own and other people's humanity and lack thereof. I just think that just seeing the symbol on someone's personal phone doesn't tell me anything. None of us know why it's there, and to say one way or the other without any context is presumptuous. Until we know his reasons from him, it's little more than a distraction imo.
I will say though that it's an odd juxtaposition seeing the Punisher symbol while standing in the hallway. My first thought would have been the Punisher would go in there and blast the shooter away, yet this guy didn't, at least not until he was removed from the scene.