Mohammed Akhlaq, 52, a resident of Bisara village in Gautam Budh Nagar, about 40km from the Indian capital, was attacked on Monday night.
He died of his injuries early on Tuesday while his 22-year-old son Mohammed Danish was admitted to a nearby hospital in a critical condition.
“My brother threw goat’s kin in the garbage dump. But some people circulated a rumour that a cow was slaughtered and an announcement was made from the local temple,” Mohammed Saifi, the victim's brother, said.
“Soon a mob of about 1,000 people, armed with lathis [baton] and swords, gathered and attacked the house of my brother.
“They did not even spare my 82-year-old mother, who has suffered injuries along with Akhlaq’s wife and daughter Sajida Saifi,” he said.
The attack on Akhlaq, a Muslim, comes as tensions increase between Hindus and religious minorities in the Uttar Pradesh state, where the incident occurred.
Beef is not illegal in Uttar Pradesh but cow slaughter is banned as the animal is considered sacred for Hindus, who form about 80 percent of India’s 1.3 billion population.
Kiran S, a senior police officer of Gautam Budh Nagar, told Al Jazeera that six suspects had been arrested over Monday night's attack.
|Relatives mourned Akhlaq [Reuters]|
India is the world's largest exporter of beef and its fifth biggest consumer but Prime Minister Narendra Modi's government wants a nationwide ban on cow slaughter and the beef trade, which is run mostly by Muslims.
Since Modi’s Bharatiya Janata Party (BJP) came to power last May, a number of attacks on minorities, including Muslims and Christians, have been linked to Hindu far-right organisations.
Last year, Hindu groups launched a campaign to convert Christians and Muslims to Hinduism dubbed as ghar wapsi [home coming], while many churches came under attack.
"The rhetoric about cow protection had emboldened some people to act as vigilantes," police officer Anurag Kumar, who is investigating the lynching, told Reuters.
"The incident is shocking," he said. "The Hindu mob felt they had a licence to kill."
Siddarth Varadarajan, the editor of thewire.in, said "the ruling party [BJP] at one level has contributed to the frenzy over the idea that cows are endangered and that they are being indiscriminately slaughtered".
"This kind of communalisation and the frenzy that has been built over the issue of beef is very unfortunate," he told Al Jazeera.
"I don’t know in this particular issue, which groups are involved but when you create a climate of hysteria then these kinds of incidents happen."
The Uttar Pradesh government, which has been criticised for not doing enough to control the recent religious unrest, announced compensation of 1 million rupees ($15,256) to the victim’s family and promised full security.
But the 20-25 Muslim families in the village are living in fear, as they had not seen this kind of violence in their lifetime.
"I screamed and shouted to tell the mob that we did not eat beef, and they should stop beating my father and my brother, but they pushed me away," Sajida, who witnessed the attack, told the Reuters news agency.
"My brother was dragged to the courtyard downstairs and they used bricks to hit him on the head and chest, leaving him unconscious. They also tried to molest me and hit my grandmother on her face. They threatened to kill me if I said a word to the police," Sajida told the Indian Express newspaper.
Police officer Kiran S said that the police were investigating which organisations were involved and how the incident happened.
"What prompted them to do this, as otherwise they lived in perfect harmony," he said.
So far, India’s prime minister has not commented on the issue.
"The prime minister has been silent for the past 14-15 months other than criticising one of his ministers. It’s unfortunate that they are not taking it seriously. The kind of cultivated hysteria is going to lead to more violence,” senior journalist Varadarajan said.