'Sons of Anarchy' Actor Johnny Lewis Found Dead -- Suspect in Bizarre L.A. Double Death

7:08 AM PT -- Law enforcement sources tell TMZ ... cops believe Johnny was on drugs-- either PCP or meth -- at the time he allegedly killed a woman and then fell to his death.

Sources tell us ... after allegedly killing the 81-year-old woman, Johnny had fought with two men for 3 to 4 minutes ... hurting at least one of them

We're told Johnny initially used a 2x4 to attack the men ... and then used his bare hands.

Law enforcement sources say the men he fought with say Johnny showed "super-human strength" and was "phenomenally strong."

We're told Johnny tried to break into the house of one of the men ... and it took 3 people to hold him back.

One source tells TMZ ... Johnny had gone to a neighbor's home to introduce himself earlier in the day.

Neighbors tell us Johnny had lived in that house before, moved away, and then came back.

Neighbors who knew Johnny say he was a "nice guy."

Johnny Lewis -- who had big roles on "Sons of Anarchy," and "The O.C." and once dated Katy Perry -- was found dead yesterday ... and his body was discovered at the same L.A. property as an 81-year-old woman he's suspected of murdering ... TMZ has learned.

According to our law enforcement sources, 28-year-old Lewis was found in a driveway Wednesday morning in the Los Feliz neighborhood -- and the elderly woman who owned the home was found dead inside ... the victim of a homicide. Investigators say they believe Lewis beat the woman to death.

According to multiple reports, neighbors heard the 81-year-old woman screaming ... and then saw a young man outside her home attack 2 other people with a piece of wood ... before he climbed onto the roof and fell to his death.

Lewis was renting a room from the 81-year-old victim.

Law enforcement sources tell us Lewis is the sole suspect in the woman's murder, and they are not looking for other possible suspects.

Lewis dated Perry back in 2006 -- and attended numerous Hollywood events together.

Lewis played Kip 'Half-Sack' Epps on "Sons of Anarchy" for 2 seasons, and also had one-off roles on "Criminal Minds" ... "Bones" ... and "CSI."