When the teacher told him to leave, police say, he pulled out the gun and shot Gunrow in the head. A few hours after the shooting, the classroom appeared frozen in time. Book bags were littered the floor, a red carnation was in a vase on the teacher's desk. Later the suspect, riding a bicycle, flagged down a police officer about a quarter of a mile from the school and surrendered. He told investigators he liked Grunow, who was popular with students.
Lake Worth is just south of West Palm Beach.
Palm Beach County is the fourth largest school district in Florida and 14th largest in the nation with more than 149,500 students. Correspondent Susan Candiotti and The Associated Press contributed to this report.