The 34-year-old had been living in Russia and studying law at Lobachevsky University since 2019, and went missing on Tuesday.
Her mother, Beccy Serou, of Vicksburg, Mississippi, had told US National Public Radio that her daughter’s last message to her read: “In a car with a stranger. I hope I’m not being abducted.”
She told NPR that her daughter was trying to get to a clinic on Tuesday and may have gotten into the passing car.
“I think that when she saw that the person wasn’t driving to the clinic, but instead was driving into a forest, she panicked,” she added.
Alexander Popov, 43, was arrested on suspicion of murder and appeared in court to be arraigned on Sunday.
Mr Popov reportedly has a record of violent crimes and faces life imprisonment if convicted.
The Russian state news agency RIA-Novosti reported that he gave Ms Serou a ride in his car, took her to the wooded area and allegedly stabbed her to death “in the course of a dispute”.
The court ordered that he was held until 15 August.
“We offer our sincerest condolences to the family on their loss. We are closely monitoring local authorities’ investigation into the cause of death. We are providing all appropriate assistance to the family,” the United States Embassy in Moscow said in a statement.
“Thank you all for your help trying to get Catherine home safe,” Beccy Serou wrote on Facebook.
“Unfortunately, we got a call from the police this morning telling us they found her body. As our family processes this news we’ll have more to say.”