A search had been underway for Catherine Serou, a 34 year-old graduate student and former Marine, after she disappeared on Tuesday in Nizhny Novgorod, a city about 250 miles from Moscow and where she was studying at a university.
Serou went missing after leaving her house in Bor, a suburb of the city, Tuesday evening and getting into an unknown vehicle, Russia's Investigative Committee, which handles serious crimes, said in a statement on its website.
Serou's body was found on Saturday, police said following a large-scale search.
A local man born in 1977 and previously convicted of multiple serious crimes has been arrested on suspicion of abducting and murdering her, according to police.
He is cooperating with the investigation, they said.
Serou had enrolled in a law masters at Nizhny Novgorod's Lobachevsky University in the fall of 2019, her mother Beccy Serou told NPR in an interview this week from Mississippi where the elder Serou lives.
She told NPR her daughter had sent her a text message on Tuesday evening just before she disappeared, saying she was in a car with a stranger.
"It says: 'In a car with a stranger. I hope I'm not being abducted.' And that's the last thing she wrote," Beccy Serou said in the interview with NPR. "
She said her daughter had been in a hurry to get to a clinic where a payment had not gone through and so had perhaps jumped into a passing car without waiting for an Uber to arrive.
"I think that when she saw that the person wasn't driving to the clinic, but instead was driving into a forest, she panicked," said Beccy Serou. "Her telephone last pinged off a cell tower in that forest."
Local volunteer groups had posted missing persons notices appealing for sightings of Serou.
Around 80 police officers and 20 volunteers from one group, 'Lynx', had taken part in the search for her, Marina Mokeyeva, one of the volunteers told the Russian newspaper RBC.
Serou moved to Russia from California after selling her condominium there, her mother told NPR.
The suspect is being investigated on charges of abduction and murder that carry a maximum sentence of 15 years prison, according to police. A decision on charges and pre-trial detention will be made in the near future, the Investigative Committee said in the statement.