Police say they have found no evidence of drugs, pending the results of toxicology tests that could take several weeks, but the actor's behavior was consistent with the psychotic effects they've seen in other designer-drug users.
Lewis, 28, is believed to have attacked his landlady on Wednesday morning at the Writer's Villa, a bed and breakfast-style house for young people working in Hollywood. Officers responded at 10:40 a.m. to reports of a screaming woman and breaking glass.
As police arrived on the scene, Lewis' body was in the driveway and Catherine Davis, 81, was dead in her bedroom. The cause of death was blunt-force trauma and strangulation. She had been beaten to death, and her cat was found in the bathroom. Police say the cat's body was mutilated.
Lewis is the only suspect in the killings, and no one else fled the scene, according to police. Eyewitnesses told police that Lewis appeared to show "superhuman strength."
"Mr. Lewis at some point jumped over a fence into a neighbor's yard, and for some reason attacked the painter who was over there painting the house," LAPD Cmd. Andrew Smith told ABC News."The painter and the homeowner were able to get him away. He jumped back into his yard where he was staying and at some point shortly thereafter fell to his death."
Smith said that there is a strong possibility drugs were involved, but at this point investigators are unsure.
Police say they have not located any drugs, and won't know for sure whether Lewis had ingested any illicit substances before his death until his toxicology report comes back from his autopsy. But they suspect that he might have been on the newest hallucinogenic synthetic drug.
"The thing we are seeing lately here in Los Angeles and across the country are synthetic designer-type drugs, something like 'bath salts', or the new one we've heard around here called 'smiles,'" Cmd. Smith said.
Known on the street as "smiles," 2C-I is sold in a powder or pill form and has a psychedelic affect on the user. The federal Drug Enforcement Administration lists it as a schedule-I controlled substance, and it is therefore illegal to manufacture, sell or buy.
Lewis was arrested Aug. 8 and had been jailed on assault with a deadly weapon and burglary charges, according to KABC-TV. He was released less than a week before his alleged rampage in L.A.'s Los Feliz neighborhood, according to jail records.
Colleagues of Lewis' say he had been leading a troubled life. Kurt Sutter, the creator and executive producer of "Sons of Anarchy," tweeted that Lewis had "unfortunately lost his way."
"I wish I could say that I was shocked by the events last night, but I was not," he wrote.