The mother of the Sandy Hook school gunman found disturbing images of dead bodies in his bedroom just two weeks before he killed 27 people.

The gruesome pictures included a drawing by Adam Lanza of a woman holding a child being shot in the back - but his mother Nancy decided not to do anything about them, according to a close friend.

One had a woman clutching a religious item, like rosary beads, and holding a child, and she was getting all shot up in the back with blood flying everywhere.

'Nancy was disturbed, really disturbed, but didn't confront him. She wanted to think it over.'

Two weeks later, Lanza shot his mother dead at home then stormed into Sandy Hook Elementary School in Newtown, Connecticut armed with her assault rifle.

He killed 20 small children and six teachers before turning the gun on himself and committing suicide.