March 1, 1947, Jeju City
Ahn Se-hun (안세) - a political activist who was a part of the independence movement during Japanese colonial rule. Later an active member of South Korean leftist political parties
Jeju residents - some 25,000 - 30,000 Jeju residents from all over the island gathered on this day at Buk Elementary School
Korean police - 330 officers from Jeju as well as 100 more dispatched from the mainland
USAMGIK - United States Army Military Government in Korea
The 28th Jeju Island 3.1 Ceremony (제28주년 3.1기념 제주도대회) officially began at 11am on March 1, 1947. An estimated 25,000 - 30,000 people from all over Jeju gathered around Buk Elementary School (북국민학교). Ahn Sehun (안세훈), the chair of the organizing committee, gave the first speech and called for the need to reject foreign powers and form a free and self-reliant democracy. Representatives for other groups followed with similar speeches giving the ceremony a decidedly pro-independence feeling.
The ceremony and speeches ended at 2pm, and a street demonstration began. The group split into two with one heading towards the inspector's office (감찰청 - predecessor of the modern prosecutor's office) and the other towards the police station and USAMGIK building located near Gwandeokjeong (관덕정). By 2:45pm the group had reached Gwandeokjeong. It was here that the incident occurred. A boy, reportedly about the age of 6, suddenly jumped from the parade and was kicked by a passing by mounted police unit (kicked by the horse). The boy crumpled to the ground while the police officer carried on without looking back.
People threw rocks after the officer and chased him, causing the officer to panic and quickly retreat to the police station. Officers at the station saw the approaching people and opened fire without warning. Four people were killed instantly and another two would later succumb to their wounds at the hospital. A further eight people were injured. Authorities would later blame a separate incident that occurred in Daegu a year earlier, when a protest turned violent and several police officers were injured, as the reason for the police's actions - many of the police at Gwandeokjeon had been dispatched from the mainland.
If April 3, 1948 was the explosion, March 1, 1947 was the lighting of the fuse that led to that explosion.
References
The National Committee for Investigation of the Truth about the Jeju April 3 Incident - "The Jeju 4.3 Incident Investigation Report"
Jeju 4.3 Peace Foundation - "Facts and Truth: Commemorating the March 1 Independence Movement" (readable here in English)
Jeju 4.3 Archives - "관덕정" (readable here in Korean)
The Jeju Massacre - "Gwandeokjeong" (readable here in English)
Jeju Dark Tours - "Gwanduckjeong Pavillion" (readable here in English)
Photo courtesy of The Jeju Massacre (thejejumassacre.com)