PALM BEACH, Florida (Court TV) — Referring repeatedly to a "storm brewing inside Nathaniel Brazill," prosecutor Marc Shiner said that the angry 14-year-old boy likely shot Barry Grunow because the teacher would not let him see a girl he liked and was giving him a failing grade. Wednesday's opening statement marked the first time prosecutors offered a motive for the killing.

But defense attorney Lance Richard derided these two possible motives, claiming that Brazill had no knowledge of his failing grade and that the boy never intended to kill Grunow, one of his favorite teachers.

Tension ran high throughout the tightly packed courtroom all morning, as the familes of Brazill and Grunow prepared for an emotional trial. Pam Grunow, the victim's widow, repeatedly rubbed her neck and shoulders throughout the proceeding. Paula Powell, Brazill's mother, often stared at the back of her young son's head at the defense table in front of her.

Brazill is charged with first-degree murder for killing Grunow on the threshold of his classroom. He was sent home early on the last day of school and, upset that he would not be able to see a girl he claimed to be in love with, returned to school with a gun. When Grunow would not excuse the girl from his class, Brazill drew the gun and after a brief standoff, shot the teacher in the face. While the prosecution claims that Brazill went to school intending to kill Grunow, the defense maintains that the shooting was accidental and that the boy only meant to scare his teacher.

The two sides offered different descriptions of Brazill's mindset at the time of the shooting.

"When Mr. Grunow saw the gun, he had no idea of the hate, the rage, the anger, the frustration" inside Brazill, said Shiner.

Brazill had a lot of powerful emotions running through him at the time, conceded Richard, but they added up to bewilderment and fright rather than hatred and bloodlust, the attorney claimed.

"He is thinking 'this is crazy', he is sweating, he can't understand why he's doing this, his hand begins to shake," Richard intoned ominously. "And he pulls the trigger."

But Shiner said that Brazill understand perfectly well what he was doing, and that he planned the murder beforehand after getting sent home from school. He began his opening statement with what he said were the defendant's own words.

"Watch, I'm gonna be all over the news. Watch, I'm gonna be all over the news," the prosecutor said, quoting a statement the defendant allegedly made to a friend before the shooting.

Opening statements were relatively short, with each side allotted only 45 minutes. Afterwards, the prosecution began its case and managed to call four witnesses before noon.

Two young classmates of Brazill who witnessed the shooting took the stand first and described the events. Though both saw Brazill cock his gun and shoot Grunow, neither were positioned to see his face or hear their conversation.

One of the girls, Shauntia Blackmon, did mention that Brazill had developed a "hit list" of students he joked about killing only months before the incident.

But during cross-examination, defense attorney Robert Udell got her to admit that the "hit list" was made only in jest, and consisted of his closest friends.

The prosecution also called Mike Mahoney, the police officer who arrested Brazill after the young boy voluntarily surrendered. The cop's testimony featured several reenactments that stirred the courtroom. In one demonstration, he got on his knees and put his hands over his head to imitate how Brazill gave himself up.

Later, the prosecution introduced the gun used to shoot Grunow into evidence and the officer showed the jury how to work the weapon. Rising up behind the witness stand, he pointed the gun at the center of the courtroom floor and loudly cocked the firearm.

The prosecution's last witness before the lunch recess was Kevin Hinds, a guidance counselor at the school who found Brazill throwing water balloons during the day, the behavior for which he was sent home.