On re-entering the country of the Grisons he was met everywhere with the cry: "Death to the Capuchins!" On 24 April, being then at Grusch, he made his confession and afterwards celebrated Mass and preached. Then he set out for Sevis. On the way his companions noticed that he was particularly cheerful. At Sevis he entered the church and began to preach, but was interrupted by a sudden tumult both within and without the church. Several Austrian soldiers who were guarding the doors of the church were killed and Fidelis himself was struck. A Calvinist present offered to lead him to a place of security. Fidelis thanked the man but said his life was in the hands of God. Outside the church he was surrounded by a crowd led by the preachers who offered to save his life if he would apostatize. Fidelis replied: "I came to extirpate heresy, not to embrace it", whereupon he was struck down. He was the first martyr of the Congregation of Propaganda. His body was afterwards taken to Feldkirch and buried in the church of his order, except his head and left arm, which were placed in the cathedral at Coire.
He was beatified in 1729, and canonized in 1745.
St. Fidelis is usually represented in art with a crucifix and with a wound in the head; his emblem is a bludgeon. His feast is kept on 24 April.