Brian was just an ordinary guy, until he was struck by the Storm and gained the ability to control Milk, which he named Lactokinesis. He went public with his power with the help of an agent, Laura, with other people, including the gang, doing the same.
They all became instantly famous. Laura started representing the gang as well as Brian and other people with powers. As more and more people with powers came forward, Brian's power became less interesting and Laura stopped representing him. Brian, who got used to the attention and started needing it, killed Laura using his power. He then killed Charlotte, Daisy, Kelly, Alisha, Nikki and Simon.
Curtis, who was lactose intollerent, used his Time Reversal power and went back in time to a point before Brian went public with his power. He stopped him from becoming famous and aborted this timeline.
However, this did not seem to negate some of the events that transpired in this timeline. After the negation occurs, Alisha has still revealed the identity of Superhoodie to Simon and everyone seems to retain their memory of the events, as evidenced when Kelly references it later when castigating Seth. Alisha's interview where she explains her power to a news reporter is shown to her by Future Simon before this episode, presumably having been brought back in time with him, even though he logically would have had to have travelled back from the main timeline in which this interview never took place (as he was dead in the "Brian's World" timeline).