How to recognize a narcissist
One of the most obvious signs of a pathological personality is some behavior that stuns you. It stuns you because it is totally unexpected. It is some reaction to something that makes you have to pinch yourself.
By that I mean, it seems a reaction to SOMETHING OTHER than the thing that caused it. Almost as if that person was reacting to a different reality than you are conscious of.
For example, let's say you see two co-workers approach each other in the hall. One smiles and says "Hello" to the other. Instead of doing what you expect (smiling back and saying "Hello" back) the other worker stiffens, clenching his fists and fiercely glaring at his greeter, as though ready to fight off an attack.
That's what I mean by a "backwards" reaction to something. It shocks you. It perplexes you. It makes you pinch yourself. This reaction is the exact opposite of what you'd expect -- and in the extreme.
The second co-worker reacted hostily to an expression of goodwill. You wonder why. You wonder if perhaps the first co-worker was mocking him with the "hello," whether there isn't some bad blood between them. You may thus assume that the first co-worker was mocking him and just puts on a phony show of goodwill when others are around. But if eventually you learn that the second co-worker gives the same backwards reaction to other people for no known reason, you should not disregard the red flag in this behavior. It is an outward sign of a twisted mind. Don't blow it off.
Again, for example, a member of a group makes an announcement that he must leave, nearly breaking down into tears as he thus says his goodbye to this community he has belonged for 20 years. He hardly has "That's all" out of his mouth before everyone in the room is on their feet and hastening AWAY from him. There are two exits to the room, and they all rush toward the the same one, the one on the opposite end of the room from him. They all are laughing and talking loudly in a dozen conversations about everything BUT what just happened.
There is something wrong with those people. In fact, there is something radically wrong with that "community." It is a cult, not a community. And the members are not in their right minds. Their knives are in his back, and that's why they're behaving like Cains.
Again for example, employee starts flattering boss, kissing up, and boss somehow takes offense at some mysterious element in what employee said, lashing out and threatening employee that he will not tolerate "that." The facial expression and tone of voice are extremely vicious, as if intentionally overdone for effect.
Everyone who witnesses the boss' bizarre reaction is stunned, perplexed. And intimidated.
Typical narcissistic shock tactics. They disarm the victim and all the witnesses, who can do nothing but gape and wonder. Unable to make sense of it, people will act as though it didn't happen, but subconsciously they will remember to fear and suck up to this boss.
Now, it can sometimes be that there has been a misunderstanding. But if there's no possibility of that, you should never discount such an episode. Normal, mentally healthy people don't do stuff like that. It is always a sign that something is seriously wrong with that person. So, don't forget about it tomorrow, when he's Mr. Nice Guy again.
If you don't get and stay away from people and groups like that, you're tempting fate.
See also Perplexing Behavior.