9/11 perps

Given the fact that many people believe that the destruction of the twin towers was a demolition job where are the people who placed the explosives etc. Are they still alive or have they been killed off, they must have families etc. if they are alive who's keeping them quite. I mean there must of been a considerable number of people involved in placing explosives/thermite etc. so where are they, could they be military personnel/CIA, people who were all ready on the inside so to speak.

Where are the people who said they witnessed a plane hitting the Pentagon, they were on the news once and were never heard of again, well at least in the UK. Were these so called witness's goverment agents who just happened to be around at the time of attack with the intention of spreading false info.