Marines on 9/11: untold story

Shortly after 9-11 I went out on a service call to a facility in the University of Central Florida complex to do a quick maintenance check on their fire system pump engines and was met at the entrance by 2 armed guards not in military attire. Very polite but they had to have an employee with clearance lead me around to all these fire suppression pump locations to check the fluids and look for any problems. Always wondered what they did there.