Sources placing his death in 407 credit him with prophesying the invasion of France by the Vandals. He notified his people of this vision, telling them to prepare. When asked if the people should fight or not, Nicasius responded, "Let us abide the mercy of God and pray for our enemies. I am ready to give myself for my people." Later, when the barbarians were at the gates of the city, he decided to attempt to slow them down so that more of his people could escape. He was killed by the Vandals either at the altar of his church or in its doorway. He was killed with Jucundus, his lector, Florentius, his deacon, and Eutropia, his virgin sister.