Soulja Boy: Shooting Incident Busts Up Birthday Party

Soulja Boy's 26th birthday bash in a recording studio came to an abrupt end when one of his guests got shot early Friday morning.

Soulja was hanging with friends, including Sean Kingston, celebrating his bday. Law enforcement sources tell us ... one of the guys stepped outside, and a male suspect wearing a mask pulled up in a car and attempted to rob the victim.

We're told a struggle ensued and the suspect shot the victim in the arm, and then fled by car. By the time police responded, Soulja Boy had bolted. The victim was hospitalized with non-life threatening injuries.

Cops don't have a suspect yet. Soulja posted pics of himself flaunting stacks o' cash during the party -- which couldn't have helped matters.

We're told Sean had already left the party when the shooting happened.