Crime scene puzzle

You are a crime investigation officer breaks into a crime 
scene. The victim is the owner  who is slumped dead on a 
chair and have a bullet hole in his head. A gun lies on the 
floor and a cassette recorder is found on the table. 
On pressing the play button, You hears the message 
'I have committed sins in my life and now I offer my soul to 
the great lord'....following a gunshot. 
What do you think is it a Murder or Suicide ? Answer with 
valid reason.