A Greek student angry at how his schoolmates treated him shot and wounded a fellow student and two workers at a training institute in Athens on Friday before killing himself, police said.
The 18-year-old gunman shot a 19-year-old at a state unemployment agency vocational school in western Athens, then fired several shots at two men working at a nearby construction site before turning the pistol on himself.
"It is the first time such a thing happens in Greece, we've never had anything like this before," Dimitris Souras, a health ministry psychiatrist supporting the victims, told reporters.
The gunman shot himself in the head and died later in hospital, a police official said. Of the three wounded in the attack, the 19-year-old student was in serious condition.
Police said the assailant, an ethnic Greek who emigrated to Athens from Georgia's breakaway region of Abkhazia, had two weapons and carried a note saying he had not been treated well by his peers.
Greece has seen a rising wave of political and criminal violence in recent months following the police killing of a teenager in December which prompted the worst riots in decades.