Then Ri Song Gye realized he could not convince Jong. On the night of April 4, 1392, he sent an assassin to Sonjuk Bridge who brutally killed Jong Mong Ju with an iron hammer. This well-known scholar advocated loyalty to the Koryo Dynasty against the usurpers. Sonjuk Bridge is located about 1 km east of Nam Gate, being situated at the south foot of Mt. Janam, which rises on the city centre. The small stone bridge dates from 1216. Later a bamboo grew up beside the bridge, and from that the bridge got his name. In 1780, the bridge was closed for all traffic and since then it is a monument.
After having got rid of Jong Mong Ju, Ri Song Gye succeeded in usurping the throne in July 1392. The stone bridge has enjoyed the attention through generations. This became a historical bridge which hastened the replacement of the Koryo Dynasty by the Ri Dynasty. At first, it was called Sonji but it was renamed as Sonjuk after his death remembering his "loyalty." The red marks on the bridge seem to be his blood.