Snowy region-Detective Riddle

Raj and Rahul were friends and their house was in a snowy region. Raj called Detective Mehul and informed him about his friend's death. Raj said he went to meet Rahul and knocked at the door but nobody opened the door. He cleaned the moisture of the window glass to look into the house. He saw Rahul lying on the floor in the pull of blood. Mehul arrested the murderer right away. How?

Raj wouldn't be able to unfreeze the window glass because its usually icy on the inside Raj wouldn't be able to unfreeze the window glass because its usually icy on the inside