As authorities work to sort out what may have led to Wednesday's shooting, those who knew Robert Butler Jr. are struggling to reconcile his final actions with their memories of the fun, outgoing student who liked to make jokes and sometimes got into trouble for talking in class.

The gunman, who had attended Omaha's Millard South High School for no more than two months, also wounded the principal before fleeing from the scene and fatally shooting himself in his car about a mile away.

“It's just unreal,” said Robert Uribe, Butler's stepgrandfather. Uribe said nothing appeared to be wrong when he talked to Butler briefly when he last saw him a month ago. He said the polite young man he knew didn't seem like a likely gunman.

“I don't know what would possess him to do that,” Uribe said.

Assistant Principal Vicki Kaspar, 58, died at Creighton University Medical Center Wednesday evening, hours after the shooting. Principal Curtis Case, 45, was in serious but stable condition.

Butler had transferred in the fall from a high school in Lincoln, about 50 miles (80 kilometers) southwest of Omaha.

An acquaintance from Lincoln, 15-year-old Justin Reynolds, said Butler had gotten into a fight with another student from his high school in Lincoln just before he moved to Omaha. The fight was off campus, but Butler's mother had sent him to live with his father because she felt like he wasn't going down the right path, Reynolds said.

Butler posted a rambling message on Facebook shortly before the shooting about his unhappiness with his new school, but he didn't supply many details. Instead, the expletive-laced note predicted Butler's friends would hear about the “evil things” he was about to do.

He wrote that the Omaha school was worse than his previous one, and that the new city had changed him. He apologized and said he wanted people to remember him for who he was before affecting “the lives of the families I ruined.” The post ended with “goodbye.” Another former classmate of Butler's from Lincoln confirmed the Facebook post to The Associated Press and provided AP with a copy of it. Conner Gerner recalled Butler as being energetic, fun and outgoing. Gerner said Butler sometimes got in trouble for speaking out too much in class, but he did not seem angry.

“He just seemed like he had a lot of energy. He liked to talk to people. He was always moving,” Gerner said.

Another friend, Jacob Edward Rinke, said he and some others had exchange Facebook posts with Butler the night before the shooting. The discussion was about cars and included what Rinke described as normal ribbing between friends.

“We were hazing each other about car stuff. He seemed fine and everything. He seemed happy,” Rinke said.

Lincoln school officials declined to provide details about Butler's student record there, but they described him as a “fairly normal, average student. Lincoln Southwest High School Principal Rob Slauson said Butler was involved in few, if any, activities.

Omaha Police Chief Alex Hayes provided no details on the weapon Butler used or how he obtained it. Butler's father is a detective for the Omaha Police Department.

Investigators were interviewing the seven-year veteran Wednesday to learn more about what may have led to the shooting.

Authorities first received reports of the shooting around 12:50 p.m. The school was immediately locked down.

Within two hours of the shooting, students were being released in groups, and when the first group emerged from the school, parents began applauding. Some students smiled, raised their hands in the air and flashed a V for victory sign.

The school on the west side of Omaha has about 2,100 students. District officials said Millard South would be closed Thursday.