NORCROSS, Ga. (CBS/AP/WGCL) -- Police in Georgia are describing a mass shooting at a spa outside Atlanta as a murder-suicide that was "probably domestic related."

Police say that surveillance video shows a man walking into the Su Jung Health Sauna in Norcross and getting into an argument, then opening fire.

Norcross police Capt. Brian Harr said that four people died at the scene and a fifth later passed away at the hospital, reports CNN.

"It's so unexpected and unbelievable," Jon Lee told CBS affiliate WGCL. Lee said his friend, the owner of the spa, was killed in the shooting spree. Lee also told the station that the shooter was the brother-in-law of the spa owner, although authorities have not confirmed that.

Harr tells The Associated Press that investigators consider the Tuesday night shooting to be more of an isolated event than a random one. Georgia Bureau of Investigation spokesman John Bankhead said the agency was using 3-D technology to reconstruct the crime scene.

Three men and two women died in the massacre, including the gunman, who reportedly shot himself. Police have not yet released the names of the victims or the shooter.