The last known sighting of 20-year-old Sudiksha Konanki, an American student from Loudoun County, Virginia, shows her “walking hand in hand with a man along the beach promenade at dawn,” just before she disappeared in Punta Cana, Dominican Republic.

Sudiksha, a University of Pittsburgh student, had traveled with five friends for spring break. On March 6, she vanished after being seen with Joshua Steven Riibe, a tourist from Iowa. A large-scale search followed, involving authorities from the U.S., Dominican Republic, and India. “This is one of the largest operations we’ve carried out for the rescue of a person,” said Agustín Morillo Rodríguez of the Dominican Republic Navy.

Initially, authorities thought she drowned due to rough waves, but suspicions of foul play have emerged. Surveillance shows Sudiksha and Riibe just before she vanished. Riibe claims he passed out after drinking and woke to find her gone. “The ocean is a dangerous place,” he told reporters.

Dominican police seized Riibe’s passport, calling him a “key element” in the case. Sudiksha’s father, Subbarayudu Konanki, urged authorities to investigate possible kidnapping or trafficking, noting she left behind her phone and wallet, which was “unusual.”