A shadowy figure

Entering the house, you can see that the lights are dimmed. The police officer guiding you has an LED flashlight, and shines it around. He guides you to the room with a dead body in the middle of it. You look around, eyeing the dead body. It is your brother, who sometimes visited your house. "Has the murderer been apprehended yet?", you ask. The police replies "No.", and you start to wonder. If the murderer was never found, and the only exit is the front door, wouldn't that mean ---

Your thought is cut off as you hear a crashing noise near the door. You look back to see, and the roof near the door has fallen in, and crushed an officer in the doorway. The light from the outside is cut off, and the police officer next to you voices his concerns. The killer must still be in the house, waiting to finish his job and eliminate you as well. You are unclear why the culprit has a vendetta for you to die. A small noise rings out, the sound of a silenced weapon. The officer next to you falls silent. In his neck, you see a bullet hole. The gunman soon turns his attention to you, and out of the shadows, you see a gun barrel pointing in your direction. A silent shot is fired, and you die. The police end up entering the building, but never find the murderer anywhere...