Apparently the "victim" was a Manure fan - reason enough in some parts of Merseyside.
As most people are, I'm surprised - Gerrard is a pretty quiet guy, more into the family life than brawling in bars. He's no Barton or Bellamy in that respect.
If I was to make a bet, Gerrard probably got in a bit of a shoving match with the guy but Gerrard's friends jumped in and did the real damage (that's pretty much what the Echo is reporting and they usually have the inside track when it comes to Liverpool).