Story highlights The gunman leaves a rambling letter titled "Doomed"

Police commissioner: The police sergeant's survival is "miraculous"

The gunman had a extensive criminal history, the commissioner says

(CNN) The Philadelphia man who went on a fatal shooting spree left an elliptical letter titled "Doomed" depicting a hatred for law enforcement but leaving few other clues about the rampage, the police commissioner said Saturday.

"It was a bunch of rantings that was tantamount to rambling so it wasn't the most lucid letter," Commissioner Richard Ross told reporters. "It was more about himself than who he wanted to harm."

Nicholas Glenn went on a deadly tear late Friday in Philadelphia, ambushing a police sergeant and firing rounds into a tavern and a car before police shot him dead, Ross said.

A 25-year-old woman died after she was shot seven times in the torso, police said. Two police officers and three others -- two men and a woman -- also were wounded.

Detectives are investigating whether Glenn was linked to or inspired by outside groups or accomplices, but so far there is no evidence that he did not act alone, Ross said. Glenn's 9mm Ruger pistol had the serial number obliterated.

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