No pun intended, but I would grill every employee in that CFA to find out what they know about this. I would start with the manager. That graffiti looks too professional and would have taken too long to do for just a couple of kids to paint it hastily overnight. Unless they were from the local art college. Which would be my next stop in the investigation. When they catch the perps, they should have them clean the side of the building with a toothbrush while the whole world watches!
You would be surprised at how quickly spray grafitti is done. This was very obviously not the first “work of outdoor art” this person has done. I was stunned at how quickly these guys can cover an entire rail car with really intricate, colorful, airbrush-quality artwork. This was just one color, a couple of different spray nozzles.... 10 minutes tops. The person is probably an illustrator in his “real life.”