According to his video testimony, he was an eyewitness to the conditions inside WTC7 from a time preceding the collapse of WTC2 to a time after the collapse of WTC1. He was interviewed in mid-2007 by Dylan Avery, director and narrator of the 9-11 documentary Loose Change, where he described his experiences of these events in detail. Excerpts from the interview were released in various online shows and were planned for inclusion in the next version of Loose Change.
"A few months later" Avery contacted Jennings, who said that he had been receiving "phone calls to his place of employment and that he was in danger of losing his job" and requested that the interview not be used in Loose Change; Avery honored his request.1
In February 2008, Avery did an interview with the BBC (which had also interviewed Jennings) and learned from the film crew that the real reason Jennings wanted the interview withheld was that he denies having said there were "dead bodies" in WTC71, which Jennings apparently did say in the video. It's unclear whether Jennings was claiming that his words in the video were misinterpreted, or that he had misspoken at the time.
When the BBC documentary featuring the newer Jennings interview was released a few days later, Avery said he felt compelled to release the full Jennings 2007 interview for reasons he explains in a 2008-07-09 blog entry.
Jennings died at age 53 on 2008-08-19 after several days in the hospital, under circumstances which some people believe to be suspicious. Very few details are currently available about the cause of death, and it is unclear whether there has been any official investigation.