Suspended student, 13, held in fatal shooting of Florida middle school teacher.(Knight Ridder Newspapers)

LAKE WORTH, Fla. _ A 13-year-old boy suspended two hours earlier for tossing a water balloon returned to school Friday, pulled out a .25-caliber Raven semiautomatic pistol and killed a popular teacher during the last period of the last day of class before summer break, authorities said Friday.

According to officials, the teacher, Barry Grunow, was shot once in the head. He died on the spot, on a breezeway at Lake Worth Community Middle School, his students just yards away. He was 35. He was married. He had a 5-year-old son and an infant daughter.

Grunow, a teacher since 1987, taught seventh-grade English literature. He sometimes rewarded his pupils with doughnuts or jokes. A banner over his desk said: "Welcome to Mr. Grunow's class."

"He was just a great teacher," said Alison Brodbeck, who was in his class two years ago. "When he read books, he used funny voices to get our attention. He'd do anything to teach us.

"He sat us by our grades. You wanted to get a good grade just to sit close to him."

Police identified the shooter as Nathaniel Brazillu, a seventh-grader said to be a good student. He flagged down a police officer and turned himself in shortly after the attack. Police said Brazill took the gun from his …