Joekatethey don't he fimlmed it just to make a documentary about suicides. I found these interesting points on wikipedia
Steel interviewed relatives of the suicide victims, deliberately neglecting to reveal that he had footage of their loved ones' deaths. He claimed that "All the family members now, at this point, have seen the film, [and are] glad that they had participated in it."[2]
The project was kept a secret in order to avoid someone who would "get it into his or her head to go to the bridge and immortalize him or herself on film." During the filming, one person jumped off the Golden Gate Bridge every 15 days on average.[3]Assuming that the rate remains steady, this means a total of approximately 24 suicides each year.
The documentary caused significant controversy when Eric Steel revealed that he had tricked the Golden Gate Bridge committee into allowing him to film the bridge for months and had captured 23 of 24 known suicides which took place during the filming phase of the project. In his permit application to the Golden Gate National Recreation Area Steel said he intended "to capture the powerful, spectacular intersection of monument and nature that takes place every day at the Golden Gate Bridge"