The mysterious sharp object-Riddle

Riddle

Someone used a sharp item to kill Gogo; his friends clarified they couldn?t have killed Gogo as they only had a music player, a water bottle, and some papers with them. How did the detective find out they were lying?

    One friend had put a piece of broken ice in the water bottle, which melted after Gogo was killed.

Mindyourlogic Riddle:  Answer:
The mysterious sharp object-Riddle