It was the last day of school before students were let out for the summer. With his class restlessly waiting for the final bell to ring in three months of freedom, English teacher Barry Grunow decided to reward his class and let them watch a movie. He chose Killing Mr. Griffin, a teen thriller flick about a group of high school students who plot to scare the wits out of a hated teacher, but accidentally kill him.

But shortly after the film ended, one of Grunow's greatest admirers and favorite students, a 13-year-old named Nathaniel Brazill, went back to the popular teacher's classroom and shot him in the head.

The shooting of a popular teacher by a promising student shocked and baffled the community of Lake Worth, Fla., which has its share of crime in its poorer neighborhoods. Now a jury drawn from the area must decide whether this killing was an accident or a cold-blooded murder.

State Attorney Barry Krischer decided last June to try Brazill as an adult for first-degree murder. "Ethically, it's my duty to charge the highest level of crime provable," he told the Miami Herald. In Florida, the charge carries a minimum sentence of life without parole — and if a jury finds Brazill guilty, the trial judge will have no discretion during sentencing.

The prospect of Brazill spending his life behind bars for a crime committed at age 13 has caused anger and raised controversy. Juvenile justice has become a hot button issue in Florida — and nationally — since the trial of Lionel Tate in January.

Barry Grunow

His mother impressed upon Brazill the importance of academic achievement, and the boy did not disappoint. He did well in school, and participated in extra-curricular activities such as band. But he wasn't just a successful student; he was also an interested one.

Grunow really liked that kind of pupil. Co-workers and family say he was a teacher who kids considered a friend, and that he loved seeing students learn but hated subjecting them to tests.

"We couldn't go anywhere without Barry's students saying 'Mr. Grunow, Mr. Grunow,'" the teacher's wife said at a news conference days after the shooting.

The two got along well, even when Brazill started slacking off at the end of the semester. Teachers and classmates say the boy went into a funk, his moods oscillating and a deep-seated anger occasionally showing beneath his usual jovial demeanor. But nobody expected what he would do on the last day of school.

Although Brazill would later return to school with a gun, in the morning brought something much more benign — flowers and a gift card for a girl he liked. The object of Brazill's affection was Dinora Rosales, and though she has since said that the attraction was somewhat one-sided, the two frequently talked and exchanged notes during school.

The last day of school was Brazill's final chance for such flirtations, as Rosales' strict Trinidadian parents would not allow her to go out with or take calls from boys during the summer. Brazill wanted to express his true feelings to Rosales before the summer break. He had written her a note a few days before, and then nervously taken it back at the last minute. This time he was intent on going through with it.

"I love Dinora. She is the sun the rain and the soil that flowers my soil (sic), I love her more than life itself," Brazill wrote on the card that accompanied his flowers.

He gave his gifts to Rosales that morning, and though she reportedly accepted them in a lukewarm manner, the prospect of romance seemed to put Brazill in a good mood for most of the day. He went about his normal routine, going to classes and talking with classmates about the end of the school year and plans for the summer.

But in the afternoon, Brazill's day took a turn for the worse. He got caught throwing water balloons by guidance counselor Kevin Hinds, and Assistant Principal Bob Hatcher decided to send him and one other student home.

Hatcher and other school officials maintain that Brazill was not visibly upset. But according to the other student sent home early, Michelle Cordovaz, Brazill told her on their way home that he was going to get a gun, return to school, and shoot Hinds.

"Just watch, I'll be all over the news," she remembers him saying.

Brazill was upset about being suspended and particularly angry that he would not get to speak with Rosales for a last time. He says he went home and tried to find his grandmother and aunt, so that they could come back to school with him and talk to the principal.

Officers crowd around after the shooting

"I didn't want to leave school early," Brazill told the Miami Herald. "I thought I'd never catch up at the beginning of next year. All my friends would leave me behind. I thought my future was ruined."

When Brazill couldn't find help, he took matters into his own hands. Putting the small gun in his pocket and jumping on his bicycle, the boy raced back to school. Brazill entered a rear building where Rosales was in Grunow's class, walked up to the door, and knocked. The teacher was surprised to see Brazill, and inquired what he wanted.

When Brazill demanded to see Rosales and another friend out in the hallway, Grunow told him that he couldn't allow him to do so and gave him a playful push. The boy responded by pulling his gun out and pointing it at the head of his favorite teacher with a quivering hand. Grunow told Brazill to put the gun away and made like he was going to close the door to the classroom.

Then Brazill shot him in the head.

"Oh shit," he said, and ran away.

Nobody disputes the facts about how Grunow was killed. Brazill admits going home, getting the gun, and, upon his return to school, shooting his teacher. Many students witnessed the killing, and a security camera caught most of it on tape.

The key questions surround why the killing occurred. The prosecution says that Brazill brought the gun to school with the intent to kill and then intentionally squeezed the trigger. Though Krischer does not have to prove motive to get a first-degree murder conviction, it will be difficult for him to win the trial without some explanation.

Student witnesses will be key elements of the prosecution's case — both from within Grunow's classroom and otherwise. The state attorney is expected to call several kids who witnessed the shooting to the stand to describe Brazill's confrontation with the teacher.

But some of the most important state witnesses won't testify about the murder, but about Brazill himself and his actions leading up to it. Cordovaz will take the stand and describe their conversation after getting sent home from school.

Brazill also showed the gun to two friends several days before the shooting. These acquaintances may testify about why he had the gone, and what he planned to do with it.

Several weapons experts are also expected to take the stand and testify that Brazill's gun did not go off accidentally. A live round was found at the crime scene with a dent in it. The prosecution has claimed this piece of evidence shows that Brazill tried to get off two shots, but that the gun misfired on the second.

After his arrest, Brazill told police that he did not intend to kill Grunow. But when asked why he brought the gun to school, the boy could offer little explanation.

"I was just mad," he said.

Defense attorney Robert Udell says that Brazill only wanted to scare Grunow into letting him see Rosales, and that his client did not mean to pull the trigger.

The defense will call witnesses to testify about Brazill's fondness for Grunow and his actions the day of the shooting.

Brazill will also have a group of expert witnesses testifying on his behalf. A psychiatrist may take the stand and talk about the boy's frame of mind.

The defense is also expected to call its own firearms expert to testify to the poor design of the gun used. Grunow's widow has sued the maker of the gun, charging it was designed without a safety mechanism.

But to win an acquittal, Udell may have to put Brazill himself on the stand to explain what happened. What the young boy might say is uncertain because he has yet to offer a complete explanation.

"It went all to pieces," he told the cops.

Brazill's future will be decided inside Judge Richard Wennet's courtroom, but there won't be any shortage of interested parties milling around outside Palm Beach County Court.

"For this sweet intelligent kid to spend his entire life in prison with no opportunities would make a tragic accident even more tragic," Udell told the South Florida Sun-Sentinel. "Surely the system can't see him as unredeemable."

"The tragedy is what happened to Barry Grunow, not what happened to Brazill," Krischer shot back in published reports.