200735
At about 11 a.m. , during the final exams , at least two eighth-grade students attacked the board of examiners with revolvers and hand grenades , killing at least one teacher , several students and themselves .
 None
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 None