The accused allegedly had abducted Shan Babu in the night and after murdering him, he carried the body to the police station on his shoulders.
Saji, who was an accused in several criminal cases, including those related to attempt-to-murder, had a dispute with his neighbour Baby’s family.
Ansil was attacked at the Canal Bund Road near his house by two persons.
The deceased has been identified as Shaji, a hotel worker.
The police had on Wednesday conducted evidence collection with the prime accused Nikhil.
SFI activist Dheeraj Rajendran, 21, was allegedly stabbed by Youth Congress member Nikhil Paili. The latter was arrested by the police later.
All the three members of the family were found dead at their house on Sunday. The dead are: Soni Zachariah, 52, his wife Reena, 45, and their seven-year-old adopted son Rayan.
The back-to-back killings of two political activists -- BJP's Ranjeet Sreenivas and the other of SDPI's K S Shan -- in coastal Alappuzha district had rocked Kerala last week.
The investigators have decided to examine all angles though Anish's family members claimed that it was a premeditated murder.
The police confirmed that Vismaya was murdered.