The 19-year-old who shot six people before killing himself was not the same young man his family knew, Geddy Kramer’s father said Wednesday.

“The person who did this at FedEx, I didn’t know,” Scott Kramer told reporters outside his Acworth home. “My son was somebody completely different.”

Geddy Kramer was quiet and liked to hike, his father said. And when he left home for work early Tuesday, Geddy Kramer gave no indication of what was to come hours later at the FedEx facility near Kennesaw.

Shortly before 6 a.m. Tuesday, witnesses said Geddy Kramer drove up to a security guard and shot him from a few feet away, leaving the man in critical condition. Geddy Kramer then entered a warehouse, where he shot five more people before turning the gun on himself, according to Cobb County police. Geddy Kramer was dead when officers arrived at the complex.

Police have declined to speculate on what may have led the North Cobb High School graduate to shoot his co-workers. One day later, Scott Kramer said his family was also struggling to understand his son’s actions.

“I don’t have an explanation. If I had one, I would try to provide it,” Scott Kramer said. “I don’t have an explanation. I don’t know if anybody can explain these things.”

Scott Kramer said his family is devastated and continues to search for clues of what was to come. He said he wasn’t aware that his son owned a gun, but investigators were able to locate evidence that Geddy Kramer bought the shotgun he used Tuesday. Still, Scott Kramer asked for the focus to be shifted away from his family and on to the victims.

“This isn’t the time for him. This isn’t the time for us. This is the time for the victims at FedEx,” Scott Kramer said. “Keep them in your prayers and wish for their speedy recovery.”

Geddy Kramer left a note behind, police said. But no details were released about what the note said and where it was found.