Plausible, but I’m betting drug use is at the root of this story:

A troubled Bronx teen allegedly in a zombie-like trance stabbed his two younger brothers and sister yesterday – and was prevented from murdering them by a Good Samaritan, authorities said.

Cops say 17-year-old Nelson Santos lost it at about 3:30 p.m. and attacked his two brothers, ages 13 and 6, and his 9-year-old sister, with a knife in their second-floor apartment in Morrisania.

Police did not give a motive for the stabbing or what type of weapon was used, but the Daily News reports Santos told cops he was “zombie-like” and used a butcher knife.

A police source told the paper the boy said he was seeing demons and neighbors said he practiced black magic.

Drenched in his own blood, 13-year-old Miguel Santos, who was stabbed nearly half a dozen times, dashed out of his living room and downstairs to call for help. Neighbor John Flores, 19, told the News Nelson Santos was screaming something about the Armageddon and chasing his younger brother with “a big kitchen knife about as long as my forearm.”

The hero neighbor wrestled with Santos as he tried to stop them; his mother, Delila, was able to grab the butcher knife out of his clutches, according to the paper.

Cops caught up with Santos outside the apartment complex and arrested him on assault charges. The distraught teen was taken to a hospital for a psychiatric evaluation, reports the News.

I’m keeping an eye on this, but I assume this will be upgraded to a Victimless Crime File. Though having lived in the Bronx I don’t rule out anything, including “possession.”