Studied at the University of Salamanca, and then at Burgos. Following a grave illness and major surgery, he became an Augustinian canon at Salamanca, joining on 18 June 1463, and making his final profession on 28 August 1464. Novice-master in the order. Definitor of his province. Prior of the order in Salamanca in 1471.
Noted for his devotion to the Blessed Sacrament; during Mass, he often saw the Host surrounded by light, sometimes had visions of the bodily form of Christ at the moment of consecration. His devotion, and his visions, often led to some very lengthy Masses. Reported to levitate during his prayers. Could read hearts in confession, and became a sought-after spiritual director. Great preacher whose sermons helped change social conditions in Salamanca.
His sermons against sinful living conditions, and in support of the rights and diginity of workers brought him the opposition of some local leaders. A duke at Alba de Tormes hired assassins to stop him, but they recognized John's holiness, and would not touch him, confessed to him, and asked forgiveness. The duke later fell ill, and was healed by John's prayers. Some local women, however, were not so concerned; when he preached against wasting resources on extravagant fashions, some of them threw stones at him in the street.
Miracles were attributed to Father John's intervention, before and after his death. One occurred in Salamanca when a small child fell into a well. The locals made every effort, but could not effect a rescue. They sent for Father John who went to the scene, laid his waistband on stone wall of the well, and prayed that the waters return the child. The well water rose to ground level, floating the child to safety. This incident is depicted in the image of Saint John on this page.
He died 11 June 1479 at Salamanca, Spain of natural causes; may have been poisoned by a woman whose lover, a nobleman, broke off their relationship after hearing John preach, and for this reason he is sometimes listed as a martyr.
