A magnesium deficiency can cause twitching in your legs, but I don’t know if anyone on the internet would be able to help tell if the pulsing sensation is caused by muscles contracting or something else.
If you have decent access to healthcare and it’s bothering you, bring it up with your doctor. It’s unlikely anyone here is qualified to be giving you medical advice. And if they were, they likely wouldn’t be comfortable giving a diagnosis based only on a post.
Yes, firing a gun in a crowded subway station is absolutely in the wrong, as we can see by the three innocent people shot, one in the head. There are police forces across the world trained to deal with assailants with deadly weapons including knives without shooting them. It’s reasonable to expect the NYPD to have the same level of training and judgement.