Three nights and four days after six killings and a suicide, the case is “over”. Police on Wednesday “officially” declared the investigation into the sordid Saturday night saga at 91/3C, Tollygunge Road closed.

“As of today, there is nothing more to investigate,” said deputy commissioner (detective department) Peeyush Pandey. “All that remains to be done is to gather evidence against the accused to be presented in court.”

The accused Pandey was referring to are Amalendu Saha — uncle of Shibendu, who killed six members of his family before hanging himself — and his wife Anita. The two have been charged with abetting the suicide.

Police sources said it was clear that no outsider was involved in the Tollygunge Road killings. So, in the police files, Shibendu goes down as the 33-year-old who plotted the death of his entire family, executed the killings and then hanged himself.

But a host of questions remain unanswered. One of the enduring mysteries will be whether there was a “suicide pact” among members of the Saha family in a financial crisis.

There are arguments both for and against this theory. Officials who stress the possibility of a suicide pact point to the fact that a soft drink bottle would not normally find its way to the family’s after-dinner table. This has been confirmed by Soma Das, the domestic help in the Saha home.

“If all the senior members of the family, without exception, agreed to have the soft drink, it must have been pre-determined,” said a sleuth.

Those who contest the suicide-pact claim that then, even Shibendu, along with the others, would have consumed the poison. But he, instead, poisoned the others before hanging himself.

“It is only when one person decides to kill the rest of the family members does he commit suicide by a different method after having wiped out the rest,” an officer said.

Also, why would Shibendu bludgeon his three-month-old son to death when it would have been so much easier to feed him the poisoned soft drink, he wondered.

Police, meanwhile, have decided to make the domestic help Soma — the only resident on the second floor of the Tollygunge address to have survived the night of horror, that saw seven deaths — and the manager of the bank that Shibendu had borrowed money from witnesses in the case.

“One witnessed the events leading to the crime that night and the other was aware of the poor financial condition of the family,” explained a police officer.