WCAU-TV, citing law enforcement sources, said the man shot himself in the chest Wednesday evening at his home. The sources said he had made several inspections of the building.
The TV station said it was not reporting the man's name pending notification of his family.
A wall of the building on Market Street came down during demolition last week, hitting the Salvation Army Thrift Store next door. Three employees and three people who were at the store to shop or drop off donations were killed.
An equipment operator who was allegedly under the influence of drugs at the time of the collapse faces criminal charges. Officials say a grand jury will investigate the disaster and determine if others should be charged.