SONS OF ANARCHY” star JOHNNY LEWIS lived a twisted life that’s been exposed in a series of bizarre journals he kept including his bizarre obsession with KATY PERRY, say sources.

“The journals are the ramblings of a madman,” said a source who knew the actor/biker. “He was a nice, decent guy but became frothing-at-the-mouth crazy and ranted in the journals about how everyone was out to get him.”

LEWIS, who dated pop star Katy Perry for 18 months six years ago, was “obsessed with getting her back,” said the source. “In his journals, he described Russell Brand as a ‘jackal’ for marrying Katy and expressed his hatred for her new boyfriend John Mayer.”

Police believe Lewis, 28, was high on the synthetic drug Smiles when he bludgeoned his 81-year-old landlady Catherine Davis to death in the Los Feliz area of Los Angeles, and viciously ripped apart her beloved cat, Jessie, with his bare hands.

“Johnny hated that cat,” a neighbor who knew both Lewis and his victim told The ENQUIRER. “He complained that its meowing sounded like John Mayer singing.”

Moments after the horrific attacks on Sept. 26, Lewis either stumbled or leaped off the roof of his rented home and plunged to his death.

It was a shocking and tragic end to a once-promising life. Lewis had appeared in 26 episodes of “Sons of Anarchy,” but insiders say he snapped after his popular character Half Sack was killed off by the show’s creator Kurt Sutter, who’s also the husband of actress Katey Sagal.

“Johnny never forgave Kurt for kicking him off the show, and in his journals he called Kurt and Katey the ‘demons from hell,’” said the source.

A longtime friend and actor who worked with Lewis on the gritty FX series added: “I think the breakdown began after he was axed from the show. He’d get this wild-eyed look and say that he’d ‘love to take them all out.’ In his sick mind, the whole world had turned against him.”

Lewis was also losing a custody battle with the mother of his love child. And in the months before his death, he had a string of arrests for violent assaults.

In fact, he was released from jail just five days before the gruesome episode.

As he deteriorated mentally, neighbors grew increasingly concerned about his landlady. “I warned Catherine that this young man was a ticking time bomb,” Kah Lin Chong, who lives across the street, told The ENQUIRER. “But she wouldn’t listen. She just told me everything was under control.”

But according to prison consultant Wendy Feldman, who worked with Lewis, he was spiraling out of control and suffered a meltdown after being dumped by his talent agency. Feldman told The ENQUIRER: “Johnny should have been put in a mental health facility where he wouldn’t have been a danger to himself or anyone else.”