He completed his first two years of theological studies in Budapest and the rest in Székesfehérvár. He was ordained a priest on July 4, 1897. In 1904, he emigrated to the United States. In 1910, he attended the execution of György Vass, who had murdered his wife. That same year, he rebuilt the church in Perty, Amboy, NJ, which had burned down. In 1934, he appeared as a witness before a special committee of the United States Congress that was investigating the spread of Nazi propaganda in the United States.​ At the hearing, Father Gross admitted that he had written an anti-Semitic pamphlet titled “Justice to Hungary, Germany, and Austria.” He claimed that the German embassy had purchased 100 copies of this publication and that the German ambassador to Washington, Dr. Hans Luther, was the work’s “sponsor, financial backer, and promoter.” The German Embassy, however, denied these allegations and stated that the ambassador had not participated in any propaganda activities. Father Gross’s appearance before the committee drew significant attention, as this was the first time the U.S. government had officially investigated the spread of Nazi propaganda in the country. He was allowed to defend himself while remaining free on $2,500 bail. In the late 1930s, he sought to establish a national church, for which he was placed on inactive status.