The final moments of Barry Season 2 featured Gene’s realization that Barry Berkman was indeed responsible for the murder, which will no doubt play a massive role in Season 3.
Barry, hoping to put his life of killing behind him, thought that if he just disposed of Janice, he could resume his newfound passion and career in acting.
Barry will presumably struggle to justify the fact that he had to kill Janice after she correctly pegged him as the killer the LAPD had been looking for.