Katerina Netolicka, 26, was found dead in her Czech Republic apartment.

The model, who had worked for Prada, L'Oreal and Elle, was found by her brother. After he called Netolicka and she didn't pick up, he became concerned and broke the door of her apartment. He found her in her bathtub, and her two dogs, who were also dead, were nearby.

Netolicka shared the apartment with her 29-year-old boyfriend, Jakub Petruzalek. She and the professional hockey player had been together for five years. Petruzalek was in Russia playing in the International Kontinental Hockey League when Netolicka was found.

An investigation is underway.

"The cause of death is at this moment unknown and we have requested an autopsy," said Lumila Svetlakova, the police's spokeswoman.

One model anonymously spoke out about Netolicka's self-harming tendencies. The model said that Netolicka displayed bipolar behavior and seemed depressed.

Adam Smrcka, a friend of Netolicka, said that she was in a good place.

"I don't really know what [happened,]" he said. "I know she stopped self-harming and was very happy with her boyfriend. Maybe she got a spasm after kickbox training, or maybe it was a stroke."

Netolicka, who had been modeling since 2004, was an avid kickboxer. She was named the Czech champion last month.

Fans have taken to social media to talk about the model's death.

One Instagram user said, "Beautiful woman. I pray there was peace in your life before you had to leave. Rest in peace."

L'OfficielNL, which is the Twitter account for Dutch Magazine L'Officiel, talked about working with the model.

"Our thoughts are with the beautiful #KaterinaNetolicka," the tweet said. "One of the best models we worked with."

L'Officiel then shared an image taken for its September 2012 issues. It featured Netolicka sitting on a car dressed in mostly black.