because i didn't think i was worthy of anything. >> graeber: it was never about anyone but charlie cullen what he did because of his own needs, his own compulsions. >> kroft: author charles graeber interviewed cullen more than a dozen times for his book, and he remembers seeing words like "paranoid," "major depression," "hostile," "passive-aggressive" and "anti-social" on psychiatric reports. >> graeber: he sees himself as a victim, and, as a victim, he's entitled to lash out in any way he wants to make things right. if that means killing patients, anything justifies his victimhood. >> kroft: you said at one point that you thought it was about power and control. what do you mean? >> graeber: if the rest of his life was spinning out of control-- if he was losing custody, if he was feeling depressed, if his love life was in the toilet-- he could poison patients, he could save patients, he could make decisions. he had an arena in which he mattered and where his actions had definite consequences. >> kroft: here you have a person who tried to kill himself at least 20 times, who is in and out o

>> it says everything about charlie cullen. he's sometimes mistaken as a mercy killer. ts mercy killer but it had nothing to do with that. >> thank you so much. charlie and i were saying it's like out of a story. >> it's just eerie. >> yeah. >>> is there one thing that may have turned tamerlan tsarnaev into a killer? his boxing coach will speak. and you'll hear tamerlan's voice for the first time. that's next on "cbs this morning." ♪ ♪ [ female announcer ] real fruit flavors. real tea leaves. and real honey. lipton tea & honey, it's all here. ♪ ♪ feel the refreshing taste of lipton tea & honey. maybe today you'll run some errands maybe another headache will get in the way. if you have migraines with 15 or more headache days a month, you're living a maybe life. and you may have chronic migraine. go to mychronicmigraine.com to find a headache specialist. and don't live a maybe life. [ female announcer ] new lean cuisine salad additions. bring your own lettuce. byol. and we'll dress it up with grilled chicken. crunchy veggies. fruits, dressings and crispy noodles. new lean