But, according to police sources, the gunman was furious because he claims that phone operators had snubbed several of his earlier calls when he phoned the Montgomery Police Headquarters in Rockville, Maryland, where the investigation is being co-ordinated. His letter even mentions some of the phone operators by name, saying they had hung up on him because they were "incompetent". It warns that because of their actions: "Five people had to die."

At least one operator told investigators she remembers the call but did not realise its significance at the time. A police source described the caller as "extremely angry," using phrases like "Just shut up and listen," or "Hear me out," and "I'm in charge."

Both the phone call and the letter also used the phrase "I am God" - first found on a Tarot card at the scene of an earlier shooting of a teenage boy.

In a chilling postscript, the gunman made a threat to include children in his next round of victims, saying: "Your children are not safe anywhere at any time." The letter, on lined paper, contained a number of spelling and grammatical mistakes, along with broken sentences.