Warning: This story contains details and images that some readers may find distressing.
CCTV footage appears to show the man repeatedly stabbing the 16-year-old as she cowers against a wall, while people walk past or stop to watch.
At one point, an onlooker appears to attempt to grab the blade from the attacker but is unsuccessful and walks away.
The girl collapses to the ground and he kicks her crumpled body, before fetching a large rock and repeatedly bludgeoning her with it.
The girl was going to attend the birthday party of a friend’s son when she was attacked, according to local police.
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The footage published on social media has been viewed millions of times and sparked an outcry from human rights groups across India.
Delhi Chief Minister Arvind Kejriwal described the killing as “very sad and unfortunate” in a tweet, saying “there is no fear of the police”.
Indian police say the teen was in a romantic relationship with the accused and the pair quarrelled hours before the alleged murder on Sunday.
The accused, named as 20-year-old Sahil, was arrested in Aterna village in Bulandshahr on Monday.
It is the latest in a series of violent incidents against women and children in India that have made international headlines and led to mass protests.