The 27-year-old woman and her 24-year-old male companion had arrived in Dehradun on October 21 to celebrate Diwali, but were reportedly missing after two days, Vikasnagar Circle Officer Swapan Kishore Singh said.
The four accused, including the cab driver Raju, Bablu, Guddu and Kundan, have confessed of raping, murdering and robbing the two victims, police sources said.
The incident happened on October 23 when the victims were returning in the taxi from the Tiger Falls about 30 km from Chakrata near here.
The body of the woman was dumped into the Yamuna river near Lakhamandal. Her friend's body was thrown from a cliff about two km from there. As there was no news about them for several days prompting, the woman's father to lodge a case in Delhi on October 29 in this connection, they said.
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The woman taught at a school in Gurgaon, whereas her friend was a resident of Dumdum in Kolkata.