WEST PALM BEACH, Fla. Jurors in the murder trial of a Florida teenager on Thursday watched a grainy school surveillance video that prosecutors contend shows an honors student pulling a gun and shooting an English teacher between the eyes, Reuters reported.

The Palm Beach county jury also heard a classmate testify that Nathaniel Brazill, then 13, asked him for a gun the day of the shooting, saying he would harm the school "because I got suspended for throwing water balloons."

"I thought he was just joking," said Brandon Spann, a classmate at Lake Worth Middle School.

Brazill, now 14, is being tried on first-degree murder charges in the slaying of teacher Barry Grunow, 35, and could face life in prison. He also faces aggravated assault for pointing the gun at another teacher and witness tampering charges for letters he wrote to friends from prison.

The teacher's killing was one of a number of prominent cases of school violence in the United States, including the rampage at Columbine High School near Denver in April 1999 in which two students killed 13 people and then themselves.

The case has also attracted attention because Brazill is being tried as an adult. Under Florida's sentencing guidelines he faces a mandatory sentence of life in prison without parole if convicted.

Two months ago, the case of 14-year-old Lionel Tate, who was sentenced to life in prison in Florida for the beating death two years earlier of his 6-year-old neighbor, sparked widespread criticism. Amnesty International said sentencing a child to life without parole violates international law.

In addition to the shooting of Grunow, prosecutors said the time-lapsed video, representing about two minutes real time, captured Brazill pointing the silver "Saturday Night Special" handgun at an unidentified female student and a teacher, John James, who testified earlier in the day.

"He said 'Don't bother me Mr. James,'" the math teacher testified.

Defense attorneys claim the gun went off accidentally and that Brazill had no motive for killing the man he called his favorite teacher. Defense lawyer Robert Udell put his hand on Brazill's shoulder during the video as the teen watched quietly.

The stationary camera that recorded the killing was placed far down the school corridor with classroom doors obscuring the view.

The video did not capture all the details of the shooting and Canadian video expert Grant Fredericks, a forensic analyst who testified about the tape, referred only to the gunman and the victim.

Brazill, dressed in white shorts, T-shirt and running shoes, is seen riding a bicycle into the school parking lot and entering the corridor where Grunow's classroom was located.

In the crucial four-second segment that captured the killing, Grunow appeared as a shadowy figure in the doorway with only his left shoulder clearly visible. Brazill is seen mainly in profile or from behind.

He appears to pull an object from his waistband, bring it toward his chest, then extend both hands with the object pointed at the victim's head. The victim falls to the ground.

The gunman lowers the object and flees before encountering James, then is shown running back through the parking lot.