Can anyone, who has been a market maker in the past (or currently) explain how a stock rushes up in a few minutes by a large percentage (e.g. VIP today, from 32 to > 33.50). I know its usually news related, but I'm wondering a) Who (mutual funds, hedge, etc.) puts in such a large buy order(s) and more importantly b) how does the market maker determine how fast to rise the price up to curd off demand. In VIP today, based on the fade after the run up, the market maker ran it up to high? I know this question is a bit basic, but I really would appreciate anyone's opinion. Thank you.