I saw a number of blue ribbons in the area today, but I couldn't figure out what they meant — until I passed by what turned out to be the house of Wenjian Liu, one of the two police officers (the other was Rafael Ramos) gunned down in their patrol car in Bed-Stuy on December 20. After seeing a little memorial sign in front of the house, I realized that the ribbons had been put up by neighbors as a tribute to the murdered officers.