Question over crazy cat

[prorescue]

About 5 months ago I noticed that Old Man (a 7 year old car I've had 2 years living with 4 other cats) makes a really distinct, but strange noise, then attacks the cat closest to him.
Example;
He sleeps on my pillow more times than not. I've woken up to him biting and pulling and my hair while making a strange noise.
EVERY NIGHT at 3-4am I hear him make this weird noise, he stands up from where he was laying, goes to the cat sleeping closest to him and bites the crap out of their neck. Causing them pain.
I've tried the pheromone collar. No longer works for him.
Can someone please tell me why he does this?
I feel as though my explanation isn't that great.
I really can't describe it other than; a crazy weird noise is made, as he positions to climb on the others and bite the crap out of their scruff. He hangs on VERY tightly to them. I literally have to pry him off sometimes by smacking his head.

 

[explodom]

Have  you  taken him  to  the  vet  recently.  Changes  in personality  can be  caused  by  illness.

 

[Norachan]

Is he neutered? It sounds like the noise an amorous male cat would make before trying to mate, especially with him scruffing the other cats.

 

[prorescue]

It does sound like their "mating call."
However, he's been fixed for 3+ years. I've read a lot of stuff saying this is a dominance issue. I feel terrible. Because he must stay locked in the spare bedroom during bedtime, as I cannot referee and sleep. Sometimes he goes for the sides of my cat(s) neck as well. Very dangerous I would assume.
I try to tell myself that even though he's locked in the bedroom alone, there are MILLIONS of homeless/sheltered cats.
If him wanting to be dominant is the case, how is that stopped and/or manageable?