Principal Sam LaCara Shot, Killed in Office at Louisiana Schnell Elementary School in Calif.

(CBS/AP) A school janitor was arrested Wednesday in the killing of Northern California elementary school principal Sam LaCara who was hailed as a role model for other educators.

No children were hurt in the late-morning shooting in the office at Louisiana Schnell Elementary School in Placerville, but one student may have witnessed the shooting, Police Chief George Nielson said.

Authorities said they arrested janitor John Luebbers, 44, at his home about an hour after launching a manhunt. Investigators were trying to determine a motive for the shooting about 50 miles east of Sacramento.

LaCara, 50, died at Marshall Medical Center.

He was called a dedicated leader by Bob Wells, executive director of the Association of California School Administrators.

"Sam has been a role model to school leaders for his dedication to students and to public schools," Wells said. LaCara had served as a treasurer of the group.

Nielson was asked by reporters if Luebbers had been laid off. The chief said that possibility was part of the investigation, but he was uncertain about Luebbers' employment status.

"There may have been some kind of dispute between the principal and the custodian," Nielson said.

Police do not believe the janitor had a criminal history.