Murder or Suicide

Judging by the scene below, can you guess whether this was a murder or a suicide?

Murder or Suicide Puzzle

This was a murder, which was supposed to look like a suicide. These are some of the reasons:

1. The dead person has not finished their cigarette yet, which is a normal thing to do when someone commits a suicide.
2. The person is left-handed, judging by the position of the pen and the lamp, but is holding the gun in their right hand.
3. It was supposed to look like the person was writing a death note before killing themselves, but it is night and the lamp is not plugged in.