Hundreds of mourners, including some teen-agers attired in punk-style fashions, packed a church in Rochester, Minn., for the funeral of four devout churchgoers who authorities believe were hacked to death by a 16-year-old family member. Two bishops and more than a dozen priests helped celebrate the Roman Catholic Mass for Bernard and Paulette Brom and two of their children, Diane, 14, and Rick, 11. The only family member spared was Joe, 19, who lived away from home. Two closed-circuit television monitors were set up in the basement of the Pax Christi Catholic Church because of the overcrowding in the sanctuary. David Brom, a high school sophomore described as a gentle boy who wrote poetry but who also favored hard-core punk music, has been charged with the ax murders.