TODAY | December 18, 2013
>> we're learning more this morning about the colorado high school student that critically wounded a classmate last week before taking his own life. this is the author of a controversial book that may have influenced the gunman speaks out. here's nbc's justice correspondence pete williams .
>> reporter: investigators say when karl pierson walked in last friday with a shotgun and more than 125 rounds of ammunition he had written on his arms with marker. on his forearm this latin phrase which means the die has been cast. he also wrote five combinations of letters and numbers which investigators say correlate to five rooms in the high school he may have been planning to attack. and now the author of a book that pierson read, the anarchist cookbook said it shouldn't be published. a classmate said he had been a fan of it.
>> he had been reading it since sophomore year and giving it to people.
>> reporter: police say he brought three cocktails to the school the day of the shooting.
>> it is a crudely drawn instructions on how to make bombs, traps and even illegal drugs.
>> it was produced at the peak of the counter culture and became something of a bible to people on the extreme left in those years.
>> reporter: and now that it's come up in connection with a school shooting , the man that wrote it said it shouldn't be p pubbished. he says it's no longer responsible for defensible to keep it in print but it's likely to keep right on selling, available on several online retailers . the publisher says there's victims of almost anything and everything and i just don't think we need to start banning books. in colorado well wishers are leaving flowers and notes for claire davis, the 17-year-old critically wounded in the arapahoe shootings.
>>> meantime, a heart wrenching imagine from that day is now emerging. a 17-year-old that survived scribbled this message to his family on his hand. i love you all so much and i'm here now. very poignant imagine.