Who is that fellow reading magazines during class?

Last week Monday I assisted two new teachers at a site across town.  I did a group lesson on large numbers asking the students to estimate the population of their city, state, country--and then the earth.  I tried to get one older fellow sitting at a table all by himself involved, but he said that he was just there waiting for someone.  As the lesson progressed, he got involved in spite of himself because he had an idea for the population of earth and no one else was eager to guess.  I sent him to the board and he correctly wrote his 6.9 billion. 

Later, I learned that he was a police officer there to guard one of the young men in the class!  I have been amused all week that he became a part of the class even if he was just there to wait for someone!