In all logic, if he travelled back in his own body 10 years earlier, the killer should also  have travelled in his own body 10 years earlier. Same. But he looks exactly the guy who killed him.  That's disturbing...

Probably he just accidentally encountered the same man who killed him in the other timeline.
As he's drunk and can't think straight he's going to attack the guy. But the guy doesn't even know who he is in this timeline, and he's just going to fight back and treat him like a drunk.

-SPOILER-

In manhwa, only the protagonist went back in time.

 Jessica:

Yes, that man looks exactly like the man from the rooftop.  If he is there did he go back with his memories intact. 

Also who was that man that was watching them in the restaurant in the grey clothing. In the trailer it looked like he was attaching the woman they were with. 

I am guessing that the man in the restaurant is watching Kim Hee A cause she is supposedly a Chaebol? Maybe a secret security? 😂