The man accused of shooting six of his FedEx co-workers before killing himself left a note behind, Cobb County police said today.

But the note’s contents weren’t released. Officer Mike Bowman said investigators also found the box for the shotgun Geddy Kramer, 19, purchased prior to Tuesday’s shootings at the facility located near Kennesaw.

“We do know the shotgun was owned by the suspect,” Bowman said.

Kramer’s father, Scott Kramer, told reporters outside his Acworth home he did not know his son owned a gun.

Police have declined to release any information about a possible motive, declining to speculate on what may have prompted Geddy Kramer to open fire, critically injuring a 28-year-old security guard. Five others were also shot.

“We’re trying to lay the foundation for what happened,” Bowman said.

Geddy Kramer was found dead of a self-inflicted gunshot wound inside a trailer at the facility. Investigators believe Kramer acted alone.

The most seriously injured, Christopher Sparkman, 28, of Canton, remained in critical condition today at WellStar Kennestone Hospital. Sparkman, a newlywed and Army veteran, was working as a security guard when he was shot Tuesday morning, according to police. A doctor told WSB that he expects Sparkman to recover from his injuries.

Two other victims, a 52-year-old woman and a 22-year-old man, were listed in stable condition this morning. Their names have not been released. Other victims have been released from the hospital, police said.

Bowman said off-duty officers have been hired by FedEx to patrol the facility as a result of the shootings. Those officers were checking employees’ identification at the facility today.