The district officials exhumed the highly-decomposed bodies from the premises of Zion English medium school.
The case dates back to February 2013, when the family head K Krupakar, correspondent of the school, allegedly killed his wife Mounika on suspicion of the latter having an extra marital affair, said Kadapa SP Naveen Gulati.
He said that the incident came to light after police arrested Ramanjul Reddy (25), a close aide of Krupakar who is also among dead.
"Krupakar had buried his wife's body on the school campus with the help of Reddy. He later hired contract killers to murder the man whom he suspected having an affair with his deceased wife," Gulati said.
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Krupakar strangulated his three children in April 2013 and buried their bodies on the school premises before committing suicide, the SP said.
However, it is not yet clear why he killed the kids.
Krupakar's father and chairman of Zion College and Zion English Medium High School, K Rajaratnam Isaac, reportedly told Mounika's mother Sujatha that the family had gone abroad though he was aware of the killings and burial of the bodies, Gulati said.
According to sources, Issac was admitted in a Chennai-based hospital and is likely to be arrested soon.