"I can only speculate over whether it would have made any difference, but I think it would have," Tove Øvermo, who worked for the Norwegian foreign office, said on the documentary "A Stepmother's Story", broadcast on TV2 on Thursday.
Øvermo met Breivik when he was four years old, the same year that psychologists concluded he should be removed from his mother Wenche Behring Breivik, who was suffering emotional and mental health problems.
Øvermo last saw her stepson on March 10th 2011, when he visited her at her home in Oslo.
She said she was shocked when the first pictures of Breivik appeared on the news after the terrorist attack on July 22nd, 2011.
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"I almost felt like I was standing outside of myself. I could not accept that this could really be true," she said.