Tragedy Mars a School’s Day in the Sun : Crime: A N.Y. student is apprehended after gunning down two classmates. The shootings occurred just before a visit by Mayor Dinkins.

A principal’s dream to show off a high school, nationally recognized for making educational progress in one of this city’s toughest neighborhoods, was shattered Wednesday when a 15-year-old student, firing at point-blank range, killed two other students before being captured.

The killings at the Brooklyn school were called one of the worst incidents of school violence here in decades. They took place less than an hour before Mayor David N. Dinkins was scheduled to tour the school.

Dinkins kept the date. Shocked and saddened, he spoke in Thomas Jefferson High School’s auditorium, issuing an urgent plea for gun control and self-control.

“It is not a good day,” the mayor told classmates of the slain students. “If this tragedy had not occurred, I would have been here saying how important it is for you to stay in school, to study hard to learn how to read and write and count and think. . . . The problem is you’ve got to survive to get an education.

“We’ve got to do everything we can to eliminate the violence, not just in the schools, not just around the schools but in the city. In large measure, the problem is guns. . . . If you don’t have a gun, you will not use the gun,” he said.

Horrified classmates told detectives that the teen-ager, whose name was withheld because of his age, pulled a .38-caliber revolver from beneath his jacket and opened fire, striking Ian Moore, 17, in the chest and Tyrone Sinkler, 16, in the head. Both died minutes after being rushed to Brookdale Hospital.

Later in the day, a 16-year-old classmate, distraught over the killings, attempted suicide. Police said the student shot himself with a .32-caliber revolver and was in critical condition at Brookdale. A police spokesman said the teen-ager was “very despondent over the deaths of his classmates.”

Sinkler’s father told reporters that his son had transferred to Jefferson in the fall because he feared violence at his previous high school. Detectives said the shooting was the result of a grudge dating back to December, but they declined to elaborate.

Extra police officers had been sent to the high school to prepare for the mayor’s arrival. Two officers were on the second floor, where the killings took place. But detectives said it happened so fast that all police officers could do was to chase the suspect, who was captured two blocks from the red brick high school building.

“He just took out the gun and instantly shot them,” a detective said. “This was a clear assassination.”

Violence is no stranger to Thomas Jefferson High School, whose principal, Carol A. Beck, won the 1991 American Hero in Education Award from Readers Digest magazine and the National Assn. of Secondary School Principals for her successful efforts to raise test scores and strengthen the curriculum.

Jefferson is in the East New York section of Brooklyn in a police precinct that recorded 109 homicides in 1990. Latest statistics show that 104 people were slain during the first 11 months of 1991--more than in many large cities. In the last five years, 35 Jefferson students have been killed, mainly in street violence. Faced with these stark statistics, Beck set up a special grieving room for students.

In November, a 14-year-old student was arrested and charged with shooting to death a 16-year-old student and seriously wounding a teacher in a hallway at the school. That killing prompted the use of metal detectors. But because of budget cuts, several other schools share the detectors, and they were not present at Jefferson on Wednesday, a Board of Education spokesman said.

Dinkins praised Beck, calling her “a magnificent woman who has done an excellent job in this school.”

“But she can not do it alone,” the mayor said. “She deserves your help.”

After she completed arrangements for extra trauma teams to be present today to counsel students, a clearly shaken Beck reflected on the killings.

“We do not celebrate the positive aspects of people, of caring and loving and just being. As a society, we don’t even seem to be interested in developing the music and the art--the sensitive parts of the human being,” she said. “As budget cuts and fiscal crises affect the city, our school system, those are some of the first things that go, that aesthetic, that undefined part of the human development.

“Sometimes, my children only hear, ‘I love you or you look handsome or you look very nice today’ in this place, in this school. From their friends, in their home, in their neighborhood, they only hear disrespectful comments. They only hear derogatory comments, things that are certainly not character building. That’s very sad.”