Answer by taking a quote from the following article:

Charles Taze Russell was born to Scottish-Irish parents, immigrant Joseph Lytel Russell  (d. December 17, 1897) and Ann Eliza Birney (d. January 25, 1861), on February 16, 1852 in Allegheny, Pennsylvania. Russell was the second of five children, of whom two survived into adulthood. His mother died when he was 9 years old. The Russells lived for a time in Philadelphia before moving to Pittsburgh, where they became members of the Presbyterian Church.

About 1870, Russell and his father established a group with a number of acquaintances to undertake an analytical study of the Bible and the origins of Christian doctrine, creed, and tradition. The group, strongly influenced by the writings of Millerite Adventist ministers George Storrs and George Stetson, who were also frequent attendees, concluded that many of the primary doctrines of the established churches, including the Trinity, hellfire, and inherent immortality of the soul, were not substantiated by the scriptures.  Around January 1876 Russell received a copy of Nelson Barbour's Herald of the Morning in the mail. Barbour was an influential Adventist writer and publisher. Russell telegraphed Barbour to set up a meeting. Barbour and John Henry Paton visited in Allegheny in March 1876 at Russell's expense so that he could hear their arguments, and compare the conclusions that each side had made in their studies. Russell sponsored a speech by Barbour in St. George's Hall, Philadelphia in August 1876 and attended other lectures by Barbour.  Among the teachings Barbour introduced was the view that Christians who had died would be raised in April 1878. Russell, who had previously rejected prophetic chronology, was moved to devote his life to what he was convinced were now the last two years before the invisible, spiritual return of Christ. He sold his five clothing stores for approximately $300,000 (current value $6,894,000). With Russell's encouragement and financial backing, Barbour wrote an outline of their views in Three Worlds and the Harvest of This World, published in 1877. A text Russell had previously written, titled The Object and Manner of our Lord's Return, was published concurrently through the offices of the Herald of the Morning. Russell was eager to lead a Christian revival and called two separate meetings of Christian leaders in Pittsburgh. Russell's ideas, particularly stressing the imminence of the rapture and the second advent of Christ, were rejected both times.

what did they do?
concluded that many of the primary doctrines of the established churches, including the Trinity, hellfire, and inherent immortality of the soul, were not substantiated by the scriptures.