Punta Cana spring break mystery: A timeline of the missing Pittsburgh student case

While her body has yet to be found, the investigation into the disappearance of University of Pittsburgh student Sudiksha Konanki reached one measure of conclusion on March 19 when Joshua Riibe, the 22-year-old college student who was seen with her the night she went missing, returned home to the United States.

Konanki is believed to have drowned on a spring break trip to the Dominican Republic, according to officials, an explanation accepted by her parents.

Nearly two weeks after the 20-year-old Konanki vanished, here's a look at the timeline of the Punta Cana spring break mystery:

March 3

Konanki and her friends arrived in Punta Cana on March 3.

March 6

In the early hours of March 6, Konanki was part of a group that went to a nightclub and then for a walk on the beach, three Dominican officials involved in the investigation told ABC News.

Most of the group went back to the hotel around 5:55 a.m. on March 6. One man -- 22-year-old Joshua Riibe, a college senior in Minnesota -- stayed with Konanki on the beach, according to a Dominican Republic investigative police report.

Authorities said they believe Konanki died by drowning, officials told ABC News.

Her missing persons case is being treated as an accident, sources said.

Authorities said Riibe is not a suspect and is cooperating and being questioned as a witness.

March 13

On March 13, when Riibe was interviewed by a prosecutor, he detailed his interactions with the missing 20-year-old.

Riibe said he met Konanki that night and said they kissed after a night of drinking, according to a transcript provided to ABC News from two Dominican Republic sources.

The two went swimming and were hit by a wave, and then they were pulled into the ocean by the tide, Riibe told the prosecutor.

"When we surfaced, we tried to plead for help, but there was no one there," he said.

Riibe, who was a pool lifeguard, said he held Konanki "under my arm and swam to get her out of the water."

"I was trying to make sure that she could breathe the entire time -- that prevented me from breathing the entire time and I took in a lot of water," he explained.

“When I finally touched the sand, I put her in front of me. Then she got up to go get her stuff since the ocean had moved us," Riibe told the prosecutor. "She was not out of the water since it was up to her knee. She was walking at an angle in the water."

"The last time I saw her, I asked her if she was OK. I didn't hear her response because I began to vomit with all the water I had swallowed," he said. "After vomiting, I looked around and I didn't see anyone. I thought she had taken her things and left."

"After I saw her walking away, while she was walking in the water, I never saw her again," he said.

Riibe said he passed out on a beach chair and woke up to the sun and mosquitoes on him. He was seen on surveillance footage returning to his room several hours later.

March 14

Riibe's parents, Albert and Tina Riibe, released a statement on March 14, praising their son's "integrity and good heart."

They said, until March 12, their son was "detained under irregular conditions and subjected to extensive questioning without the presence of official translators or legal counsel."

"We recognize that this is a complex and painful situation for all parties involved, and we trust that the investigation will be conducted with transparency and justice," they said.

"We express our deep sorrow and solidarity with the family of Sudiksha Konanski during this painful time," the parents added. "Above all, we wish to contribute to the search efforts and understand the anguish and uncertainty they are going through and we share the hope that Sudiksha will be found as soon as possible."

March 15

Joshua Riibe was questioned extensively on March 15, with his lawyers present, an official close to the investigation told ABC News. The 22-year-old also went to the beach with investigators and his lawyers, the source said.

March 17

On March 17, Joshua Riibe's lawyers said they've requested a habeas corpus hearing, according to a source from the Dominican Republic Ministry of Justice.

Joshua Riibe was questioned by prosecutors over three days, and his lawyers believe he's being detained illegally and want to prevent him from being placed in custody, an official close to the investigation told ABC News. Authorities have confiscated Joshua Riibe's passport and his attorneys said he's being surveilled at his hotel.

In the Dominican Republic, people can challenge an unlawful detention through a habeas corpus hearing. Detained individuals are required to be brought before a judge within 48 hours, or they must be either charged or released.

The same day, according to sources close to the investigation, Konanki's parents sent a formal request to Dominican Republic officials, asking them to declare their daughter dead.

In the same letter, they said that they understand that certain legal procedures must be followed for their request, but that they are prepared to comply with any necessary formalities or documentation, sources said.

The sources also explained that her parents acknowledged in the letter that there is no suspicion of foul play in the incident regarding their daughter's presumed death.

March 18

During his habeas corpus court appearance on March 18, Riibe said he was "ready to go home and go back to my life."

The request was granted, effectively removing Riibe from police surveillance -- but the court declined to return his passport.

The judge is expected to decide if he will be charged with anything or can leave the country on March 28.

Additionally, the Dominican Republic Civil Defense said that it was scaling back its search-and-rescue efforts in the case.

March 19

Early March 19, Riibe's legal team confirmed to ABC News they were trying to obtain a new passport from the U.S. Embassy in the Dominican Republic so he could leave the country.

"The U.S. Embassy is in communication with Mr. Riibe, his family, and his lawyer and is providing all appropriate consular assistance," the U.S. Embassy in the Dominican Republic told ABC News.

Later in the day, a source from the prosecutor's office said Riibe would receive his passport back on Thursday.

However, Riibe's legal team confirmed he obtained the emergency documents instead of waiting until Thursday and returned to the United States late Wednesday.

ABC News' Erielle Reshef contributed to this report.