I'm surprised I can't find a website dedicated to the history of Pach Bros. - small collections in the Library of Congress and the Smithsonian, and a nice history here
http://dlib.nyu.edu/findingaids/html.../bioghist.html which says:
A dramatic fire on February 16, 1895 completely burned out the Pach studios that were located on the top floor of the buildings at 935 and 937 Broadway. An account in the New York Timess (February 17, 1895, p. 17) stated that there were thirty employees at work in the studio, and twenty patrons sitting for their portraits, when the fire started in the negative retouching room. No lives were lost, though all negatives created in the New York and the college satellite studios from the time of the firm's founding were destroyed.