Suicide - the graph on the wall shows a massive decline, and since it showed a largely positive trend up until then, you can assume that’s bad. He’s got an empty glass, and the bottle’s broken on the other side of the room under a wet patch on the wall, suggesting he threw it (out of frustration), which would explain the rest of the mess being within throwing/kicking distance of the chair. The gun is also at the same angle as his hand, and his trigger finger extended further than the rest, suggesting it slipped out when his body went limp.
Definetly a murder, if the guy in the background running away and the open window are not enough, there is also a sign of a struggle. More importantly there are no 'comforts' people who commit suicide have comforts around them to encourage them. He was also half way through doing something. Finally, bleeding is on the right side of the face which indicates the gunshot would came from the left, but the gun is on the floor next to the right hand.
It really could go either way. Windows open could mean he was just trying to get some air. He could’ve shot him self. The guy out there could have been playing soccer for all we know. Notes could be for someone before he took his life. The room all messed up could’ve been from him being angry and destroying the room. If he was fighting with the other guys I doubt it he would’ve die in his chair that seems odd. it appears to be a bottle of liquor thrown against the wall below the air conditioner. so im not saying your wrong but i wouldnt say def murder. my guess is self inflited. in another note you sent that guy to prison for life and he just happend to be running by at the time of the picture.