"Malvo has been pretty forthcoming and credible ever since he's beein in prison," Tracy said.
Malvo told Shatner Muhammad took him in and trained him when he was a teenager to be a coldblooded killer.
"He would send me to do a crime and then he would watch the crime and then he would evaluate me after I would finish and we'd work on the next time what was wrong, what I needed to change, emotionally, in my approach, in my tactics," Malvo said of Muhammad, a man his defense lawyers once called a "monster." Shatner told "Good Morning America" Thursday that he believes Muhammad brainwashed the teenager.
"He was a malleable teenager and lacking love in his life," Shatner said. "John Muhammad supplies the love and influences him to become a killer, and he becomes a cold-blooded killer at the age of 17. Now he's in jail and now he begins the turmoil in his mind."
Malvo, who lives in segregation at a maximum security prison, told Shatner he has forgiven Mohammad and himself.
"This is going to be surprising, but I've had to forgive him in the same way in which I've had to, over time, gradually forgive myself," Malvo said. "Every day I get up, somebody's wife, child, husband is not going to come home tonight. There is nothing that I can say or ever do that will ever change that fact."
The Associated Press contributed to this report.