Final answer:
Between one thousand five hundred to two thousand people participated in the Kent State protest which ended violently with four students killed by Ohio National Guardsmen gunfire.
Step-by-step explanation:
Approximately a few thousand people participated in the Kent State protest. Specifically, tensions escalated on May 4, 1970, when campus officials had called off a planned demonstration, yet around one thousand five hundred to two thousand students assembled, leading to tragic events. Ohio National Guardsmen fired into the crowd, resulting in the death of four students and wounding nine others. The size of the protest at Kent State compared to other protests during the same era, which often saw tens of thousands of participants, underscores the magnitude of the response to the shooting and the national divide it represented.