INCHEON -- Police referred a university freshman accused of raping a schoolmate and causing her to fall to her death to the prosecution Friday for potential indictment with an additional charge of filming the rape scene, officials said.

"I am sincerely sorry," said the 20-year-old student of Inha University in Incheon, west of Seoul, as he was transferred to the prosecution, without responding to questions from reporters, including on whether and why he did not help her immediately after the fall.

He was detained by police last Friday hours after the victim was found dead apparently after a fall from a campus building. She was found lying naked on the ground at 3:49 a.m. reportedly with blood on her head, mouth and ears.

The suspect allegedly drank together with her and others before he and the victim left the group, saying he would escort her back to school. Closed-circuit TV footage showed the suspect assisting her as they went inside the building at around 1:30 a.m.

Police believe he raped the victim in the school building and caused her to fall to her death from the third floor before he threw away her clothes at a distant place and ran away from the scene.

Investigations have shown she was left alone for over an hour after the fall and could have been saved if the suspect had immediately come to her help.

Police said they could not charge the suspect with murder due to a lack of evidence.

But they pressed an additional charge against him of filming the rape scene with his mobile phone, though only sound of the scene was recorded in the video, the officials said.

During the previous police questioning, the suspect acknowledged the victim fell to her death but denied he pushed her off the building.

He was referred to the prosecution for further investigation and indictment. (Yonhap)