Unsolved Enigma: "I may have done it."

In that night, who could have possibly murdered Sabine?

"No signs of forced entry or a struggle or any plausible murder weapons or anything taken here." An inversigator said the following day to his companion, scanning the crime scene with his sharp eyes pointing at particular places surrounding the crime spot. "Sir, we have no leads. Everything looks perfectly normal. We've covered the whole area and there were no traces. Swabs and other samples were taken to the lab."

The investigator sighs and looks around for the last moment before setting foot back to the head quarters. "I'll inform detective Khael."

"No need. I'm here. I came as soon as I heard." Khael stepped in and takes a look around casually. "Where is she?" he whispers to the investigator still taking in what he could see. "Sir, she was taken for autopsy. A man named Gabriel found her this morning."

After taking in what he saw, he whispers "I see, I'll have a word with him. Thank you." then sets foot to the front door. He casually gazes up the house as he was out; its was plain and quite ordinary.

"Detective?"

"Hmm?" Khael looks up from the initial report before investigation.

"Did you know her?"

"Know who?"

"The victim. The girl that is named Sabine." his secretary said pointing at the picture on the topmost left corner paper clipped to the document.

"Yes. But we are no longer what we used to be."

He walks to his car, feeling the chill on his back as he remembered the conversation with his secretary earlier that day. "No longer what we used to be.... What was I to her?" At that moment, he notices a letter on his windshield in an elegant red envelope. Reluctantly, Khael gets out of the car and takes the small envelope, feeling it. He opens it and in an instant, an ominous feeling crept over him. "Do you believe in fate, detective?" it said.

"Do you believe in fate, detective?"

~note, this is part 2 of the story~