Transcript for Security guard arrested in death of US tourist in Costa Rica: Police

We'll turn to the alarming headline involving an American woman on vacation in Costa Rica. Authorities say they've now found the body, and that it was murder. Now comes word tonight of an arrest. Here's Eva pilgrim. Reporter: Tonight, an arrest in the death of American Carla Stefaniak, who vanished while vacationing in Costa Rica. Police say they've arrested a security guard, bismark Martinez, who lives next to the airbnb where Stefaniak was staying. Second day. Reporter: The body, found in the woods nearby, was stabbed to death. Police believe it is sefaniak, but they will now work with the FBI to make final identification. The 36-year-old, who was celebrating her birthday with her sister-in-law, decided to stay an extra day alone, checking into the airbnb, this picture of the room, the last she would send her family. Texting, "It's raining hard and the power went out. Super sketchy." Before her phone died, she said she was going to ask a guard for water. Stefaniak's family and friends, now in Costa Rica, have been pushing for answers. Right now, emotions are taking over because there's not much we can do. We're just waiting for that phone call that we can go back to the morgue. Reporter: David, authorities say they found blood in her room at the airbnb, and the guard became a suspect when his story didn't match what they found on security cameras.

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