[[File:NYP LOC5.jpg|thumb|right|[[Pennsylvania Station (New York City)|Pennsylvania Station]]]] His first two bombs drew little attention, but the string of random bombings that began in 1951 frayed the city's nerves and taxed the resources of the [[New York City Police Department|New York City Police Department (NYPD)]]. Metesky often placed warning calls to the buildings where he had planted bombs, but would not specify the bomb's exact location; he wrote to newspapers warning that he planned to plant more. Some bombs came with notes, but the note never revealed a motive, or a reason for choosing that particular location. Metesky's bombs were gunpowder-filled [[pipe bomb]]s, ranging in size from long and from in diameter. Most used [[timer]]s constructed from [[flashlight]] batteries and cheap [[pocket watch]]es. Investigators at bomb sites learned to look for a wool sock – Metesky used these to transport the bombs and sometimes to hang them from a rail or projection. Between 1940 and 1956, Metesky planted at least 33 bombs, of which 22 exploded, injuring 15 people. Metesky's first bomb was crude, a short length of brass pipe filled with gunpowder, with an ignition mechanism made of sugar and flashlight batteries. Enclosed in a wooden toolbox and left on a Consolidated Edison power plant window sill, it was found before it could go off. It was wrapped in a note written in distinctive block letters and signed "F.P.", stating   Some investigators wondered if the bomb was an intentional [[dud]], since if it had exploded the note would have been obliterated. In September 1941, a bomb with a similar ignition mechanism was found lying in the street about five blocks away from the Consolidated Edison headquarters building at 4 Irving Place. This one had no note, and was also a dud. Police theorized that the bomber might have spotted a police officer and dropped the bomb without setting its fuse. Shortly after the United States entered [[World War II]] in December 1941, the police received a letter in block capital letters:  True to his word, Metesky planted no bombs between 1941 and 1951, choosing instead to send crank letters and [[postcard]]s to police stations, newspapers, private citizens and Con Edison. Investigators studying the penciled, block-lettered messages noted that the letters "G" and "Y" had an odd shape, possibly indicating a [[Europe]]an education.