A 50-year-old man was beaten to death, while his 22-year-old son was severely injured in Uttar Pradesh's Dadri after it was rumoured that the family had been storing and consuming beef, police said.
Muhammad Akhlaq and his son were beaten allegedly by residents of Bisara village, Indian Express reported.
The attack on Akhlaq and his family occurred around 10pm on Monday night, after a local temple allegedly announced the family had been consuming beef.
Farm worker Akhlaq succumed to his injuries, while his son Danish was admitted to a government hospital in what doctors called "critical" condition.
Violent protests erupted after six people suspected of involvement in the incident were arrested near Delhi.
Bisara village sarpanch Sanjeev Kumar Rana ─ who also runs a shop near the temple ─ claimed the temple priest and an aide were among those arrested.
Police said the priest was released after questioning.
Senior Superintendent of Police (SSP) Gautam Buddh Nagar Kiran S said that preliminary investigations revealed an announcement had been made from the temple about the family consuming beef.
"The priest was picked up for questioning as we need to investigate the involvement of others in the case," he said.
He said that a case of rioting and murder had been registered against 10 people, of which six had already been arrested. Rupendra, vivek, Sri Om, Sandeep, Saurav and Gaurav, who are all residents of Bisara village.
The SSP said police had been told of a group of people entering the temple and using a microphone to make the announcement. "However, investigations are still underway. We do not know if any of the accused are associated with the temple."
Akhlaq's 18-year-old daughter Sajida said the family kept "mutton in the fridge", not beef.
She said a group of over 100 villagers arrived at the family's home. "They accused us of keeping cow meat, broke down our doors and started beating my father and brother."
"My father was dragged outside the house and beaten with bricks. We came to know later that an announcement had been made from the temple about us eating beef,” she said.
Samples of the meat were sent "to the forensics department for examination", police said .
Gautam Budh Nagar District Magistrate N P Singh said police had been deployed in the area and the situation was under control.
"Some locals spread rumours that Akhlaq had cow meat at his home and engaged in cow-slaughtering," he said, adding "Following the rumours, tension ignited and some locals attacked his home in Bisara village."
Residents of Bisara and nearby villages clashed with police following news of the arrests. Protesters damaged vehicles, including a police van and a motorocycle.
One man, Rahul, was injured as police resorted to firing.
His brother, Narendra, said, “Around 500 protesters from nearby villages had assembled there. A policeman fired a shot in the air but it hit Rahul on the side of his abdomen."
Senior police officials contested Narendra's version. SSP Kiran said "We are yet to ascertain the type of bullet and the weapon from which it was fired."
Many Hindus regard the cow as the living symbol of their religion. Hindu welfare organisations run gaushalas, or cow shelters, in many cities where abandoned cows found wandering the streets are given food and shelter. Feeding a cow is seen by many Hindus as a way to appease the gods and get one’s wishes fulfilled.
Not all BJP-led states are pushing for tighter restrictions on beef. The chief minister of Goa, another BJP-led state, has refused to back the ban, saying that two-fifths of people there eat beef and he respected the rights of minorities.
Meanwhile, Hindu nationalist groups affiliated to Modi's BJP want to set up more cattle camps and cow shelters to house animals no longer wanted by farmers. India has some 300 million cattle, and animals foraging for food are a familiar sight on the rubbish-strewn streets of towns and villages.