After his brother was murdered in anti-Muslim riots, Pervez Qureshi watched the videos he believes incited the killers, part of a wave of hatred being fomented on social media ahead of India's elections.
India has a long and grim history of sectarian clashes between the Hindu majority and its biggest minority faith, but analysts warn increasingly available modern technology is being used to deliberately exploit divisions.
"Videos and messages were shared on Facebook and WhatsApp which contained inflammatory language and incitement to violence," Qureshi told AFP, recalling the attack on his brother Faheem in February in the northern city of Haldwani in Uttarakhand state.
"It poisoned the atmosphere."
According to figures from the Internet and Mobile Association of India, nearly 550 million more Indians have access to the internet than when Prime Minister Narendra Modi came to power a decade ago.
Modi's Hindu-nationalist Bharatiya Janata Party (BJP) is widely expected to win a third term in elections that begin on April 19.
Part of his popularity can be attributed to his party's masterful online campaign team, staffed by thousands of volunteers who champion his good deeds and achievements.
Modi's use of social media "awakens nationalism and patriotism among the youth in every corner of the country", said Manish Saini, a youth leader of a BJP "IT Cell" in Uttarakhand state, who works online to reach voters.
'Atmosphere of hatred'
Critics, however, accuse the BJP's sophisticated social media apparatus of fanning the division's flames.
Haldwani community leader Islam Hussain said tensions were already high before February's violence, after months of incendiary social media posts calling Muslims "outsiders".
"It was said that due to the increasing population of Muslims, the social demography of Uttarakhand is changing", Hussein said.
"Right-wing social media cells have a big role in creating an atmosphere of hatred against Muslims."
Clashes erupted after the authorities said a mosque had been built illegally, and a Muslim group gathered to prevent its demolition.
Some hurled stones at police officers, who beat them back with batons and tear gas.
Hindu residents gathered to cheer on the police clampdown, chanting religious slogans and throwing rocks at the crowd.
Footage of the riots spread swiftly on social media.
Egged on by online calls to mobilise, Hindu mobs rampaged through the streets.
"It's time to teach them a lesson," read the caption to one of dozens of inflammatory posts, many of which remain online.
"The time has come to beat Muslims."
Qureshi said his brother Faheem, 32, was killed by Hindu neighbours after they first torched his car.
'Triggers an incident'
But Saini, coordinator for the BJP's youth wing, said the online team he leads does not encourage violence -- and is under strict instruction not to "write anything against anyone's religion".
He said his colleagues had mobilised quickly on the day riots broke out to provide information, not to stir up trouble.
"When we got the news, we immediately started preparing graphics, videos and text messages to reach people with the correct and accurate information related to the incident," he said.
He said the initial violence was clashes between police and a Muslim group -- and blamed Modi's opponents for instigating riots to tarnish the government's image.
Critics disagree.
Raqib Hameed Naik, from the research group Hindutva Watch, said that the BJP's IT Cell had generated anger towards minorities by promoting the government's Hindu-nationalist agenda.
Naik, who documents hate speech against religious minorities, said the social media messages spreading during the Haldwani violence followed a pattern seen in previous riots.
"First, hate speech against Muslims by a Hindu activist or politician creates an atmosphere... then the hate speech triggers an incident," Naik said.
Afterwards, online Hindu-nationalist campaigners "hold Muslims responsible" for the violence, he added.