Costa Rica's government spokesperson Walter Espinoza said the guard was identified as 32-year-old Bismarck Espinosa Martinez, a Nicaraguan who immigrated to Costa Rica in June.
On November 27, the night before she was supposed to fly home, Stefaniak texted her sister-in-law, April Burton, to say that her AirBnB location was "sketchy". A Gofundme account says Stefaniak was last heard from around 8 p.m. on November 27.
According to Gardner, Stefaniak texted her family updates and photos throughout the late afternoon. Her father caught a flight from Tampa International Airport on Monday - not long before authorities in Costa Rica made the grim announcement that an unidentified body had been found not far from the Airbnb.
Espinoza shared no details on what police uncovered, other than to say they have reviewed surveillance footage and interviewed anyone they could find who had contact with Stefaniak.
The man arrested for the killing had worked at the apartment complex, the station said. They believe she was kidnapped. When she never exited her scheduled flight Wednesday, her family began worrying.
"All the data we've compiled points to this being her; however, we want a determination that is more precise, more technical and more scientific", said Espinoza.
After her disappearance, he traveled to Costa Rica to work with authorities and retrieve his missing sister.
Authorities found Stefaniak's body around noon Monday in a wooded area of the San Jose neighborhood of San Antonio de Escazu.
"We are all still waiting for confirmation", reads a Tuesday message on the Finding Carla Facebook page.
The identity was determined after the body was excavated and an autopsy was conducted. At this time, authorities have not been able to confirm that the body is Stefaniak.
"Words can not express how shocking and devastating this is to her family and her friends", Antonieta wrote on Facebook. "Exercise normal precautions in Costa Rica". The next day, Stefaniak failed to show up for her flight home and hasn't been heard from since.
Another brother, Carlos Caicedo, previously told WFLA that he's in Costa Rica, saying he visited the Airbnb and elaborated on what the guards had told him.
"It was her birthday, and it makes me feel really bad". US Embassy in Costa Rica and Federal Bureau of Investigation is already alerted.
"'I'm just gonna go ask the guards to buy me a bottle of water.' He says that her phone died, and that's it", Burton said. "We checked her email and she did not take an Uber at 5.10am".
Then the guard told a different story: It wasn't an Uber. Later that night, all communication stopped.
"He tried to Facetime her twice and he couldn't get through", Jaime said.