In India and Pakistan, laddusball-shaped sweets made of flour, minced dough and sugar, are for special festive occasions, like holidays, weddings and births. And on a Wednesday in mid-April, Umar Hayat and his family had much to celebrate in his village in Pakistan’s Punjab province, the birth of a grandson, Abdullah.

According to the newspaper Dawn, he invited scores of relatives to his small mud hut in Karor Lal Esan, dispatching his son in advance to buy five kilograms (about 11 pounds) of the treat, enough to serve everyone. Of course, they gobbled them down, especially the children.

But as they did, they started vomiting, one after the other, in quick succession. They were rushed to the local hospital, Dawn reported, where they only became sicker. Then, one by one, they started dying. By Thursday of that week, 12 members of Hayat’s family were dead, among them eight sons, a daughter and three grandchildren.

At the same time, several dozen others who had purchased sweets from the same Tariq Hotel and Sweet Shop, also took horribly ill and were rushed to the hospital. By this week, 19 more who had consumed the sweets were dead.

The tragedy became a great mystery.

Rameez Bukhari, a senior police officer from the local district, suggested that a worker at the shop “inadvertently” added pesticide to the laddus mix. “There was a pesticide shop close by which was being renovated, and the owner had left his pesticides at the bakery for safe keeping,” Bukhari was quoted as saying by Gulf News.

“A baker may have used a small packet in the sweet mixture,” he said, but added that police were awaiting the results of laboratory testing.

The Chief Minister of Punjab paid a visit to the village, assuring the locals there would be a thorough investigation.

Local health officials shut down the shop and sent samples to a laboratory in Lahore.

Friday, Dawn and other news outlets reported that the mystery was solved. Authorities finally tracked down the alleged cause of the mass poisoning when the younger brother of the sweet shop’s owner confessed that he had spiked the sweets with a pesticide. He wanted “to teach him [his brother] a lesson,” he reportedly told police.

The 18-year-old, identified as Khalid Mahmood, reportedly claimed his brother had “tortured him” and “insulted him on every trivial thing,” according to Pakistan’s SuchTV.

According to media reports in Pakistan, Khalid said that he laced sweets with a poison named Chlorfenapyr. Police recovered an empty bottle of the chemical hidden in sunflower fields on the information provided by the accused, reported Abb Takk TV.