Black tar vomit usually means bleeding from the stomach such as with a stomach ulcer. I wonder if his drink has been contaminated with something?
The other cause of bleeding after vomiting is when there is a tear in the esophagus from excessive vomiting which causes bleeding from blood vessels.
These symptoms call for an urgent visit to ER for investigation. Any samples of the vomit and the affected drink/glass should also be taken if possible.
If the drink was contaminated with a mood altering substance then that could explain the change in behavior, he would need some blood tests to clarify this.
The other common reason for change in behavior is a hypoglycemia attack where the blood sugar drops really low but this would mainly occur in insulin dependent diabetics who had been drinking without adjusting their insulin levels.
Although unlikely in his age, a problem in the brain could also cause this sudden change too.
You must check that he is getting medical care right now.
If the doctors are saying that he is non responsive then he is unconscious and not responding to the usual stimuli or to immediate treatment. It means that his body has shut down in order to try to repair itself. It could mean that he is very ill and that whatever has triggered this episode has been very toxic. If his friends have any idea what may have been taken that could have mixed with the alcohol to trigger this then they must let his doctors know. The hospital will run blood tests but it will be a while before the results come back and until the doctors know for sure what the cause is, there is only symptomatic treatment that they can give.
So they can keep an eye on his breathing and heart rate but you need to wait until they can tell you more. Its going to be a worrying time for you.