Actually, to me that was a big CLUE that the mysterious men may be "international" in origin.
TRAINS
Train With Sulfuric Acid Derails in (Illinois)
http://www.chron.com/disp/story.mpl/ap/nation/3724879.html
Five hurt in train crash (London)
http://www.news.com.au/story/0,10117,18478292-23109,00.html
Train fire causes commuter delays (New Zealand)
http://www.newstalkzb.co.nz/newsdetail1.asp?storyID=91787
Two dead in Italian train collision
http://www.wluctv6.com/Global/story.asp?S=4631714&nav=81AX
Maybe the unidentified two at Davis-Monthan AFB were in a hurry to look at the new Predators stationed there.
http://209.157.64.200/focus/f-news/1597116/posts