Sebastian was the son of a wealthy Roman family. He was educated in Milan and became an officer of the imperial Roman army, and Captain of the Guard. He was a favorite of Emperor Diocletian. During Diocletian’s persecution of the Christians, Sebastian visited them in prison, bringing both supplies and comfort. He is reported to have healed the wife of a fellow soldier by making the sign of the cross over her. During his time in the army he converted many soldiers and a governor.
Charged as a Christian in 288 in Rome, Sebastian was tied to a tree, shot with arrows, and left for dead. However, he survived, recovered, and returned to preach to Diocletian, where the emperor then had him beaten to death.
During the 14th century, the random nature of the black plague caused people to say that the plague was introduced to their villages through being shot by natures archers. In desperation they prayed for the intercession of a saint associated with archers, and Saint Sebastian became associated with the plague.
Special Thanks to the Catholic News Agency for supplying the information on this saint.