On June 19, around 7 p.m., four police officers from the Sathankulam station arrested the father and drove him away in a van. When his son rushed to the police station, he was detained as well.

Several witnesses, including a lawyer, Raja Ram; one of the Jeyarajes’ neighbors, Dev Singh Raja; and a rights activist, Yusuf, who like many Indians uses only one name, said that when the men were brought to a hospital for a medical exam the next day, they were limping in blood-spattered pants, leaving a trail of thick, dark blood. Ponraj Jeyaraj asked for a lungi, a type of sarong. His son, too, changed into fresh clothes.

Paramedics watched in shock, Mr. Ram said, as the Jeyarajes’ new clothes reddened with blood within minutes. The father and son were then driven to the house of a magistrate, who saw them from a distance and gave the police permission to send them to jail.

On June 22, they were moved to a hospital after complaining of chest pains. Ponraj Jeyaraj was the first to die, late that night. Hours later, his son died.

After shopkeepers called for a strike to protest the deaths, the Central Bureau of Investigation, a federal agency, stepped in. Ten police officers have been arrested and put in jail, but a magistrate told prosecutors that none of the officers were cooperating and that they had tried to destroy evidence.

These days, the Jeyaraj family spends much of its time meeting with investigators and trying to obtain the autopsy report, a process that is likely to take months.

“Getting justice in cases like these is a long struggle,” said Vinod Kumar, a son-in-law of Ponraj Jeyaraj. “Especially when you know the protector has turned into a murderer.”