The abductors of the two kids, who were kidnapped five days ago and whose bodies were found on Saturday, had been closely following the police and the victims' family.
"They were keeping an eye on our every move," said Amit, a relative.
"They knew about police teams visiting our house, keeping watch in private vehicles outside. They seemed to know everything, including how and from we were arranging the ransom."
The family of the abducted and murdered siblings claimed the local police had failed on each successive step, as far as the technical aspect of their investigations was concerned.
"In all, we received more than seven ransom calls which the police weren't able to track in time," claimed Rajender, one of the victims' relatives. "Later, they were found to have been made from different PCOs, located within a kilometre of the house."
According to police, the calls were found to have been made from PCOs located at Laxmi Nagar, Ganesh Nagar and Pandav Nagar. This gives currency to the family's claims that an insider might be involved in executing the crime.
Sources said investigators were also unable to glean any worthwhile clue from a network of CCTV cameras installed across the private school from where the children were abducted on the fateful day.
Meanwhile, one of the prime suspects in the case, the landlord's son Vivek, was overzealously assisting the family in collecting and accounting for the ransom amount.
"Despite having told them that we suspected his involvement, the police took him for questioning a day after the children went missing. They just kept giving us false assurances and now the children are dead," said Vijay Pal Singh, the siblings' grandfather. The police refuted allegations of laxity and claimed they were close to cracking the case.