Robert De Niro is still mourning the death of his grandson, Leandro De Niro Rodriguez .

The actor shared as much in an interview with People published Wednesday and said he was in disbelief when he heard the awful news.

Rodriguez died from an accidental overdose in New York City last summer at the age of 19. He was the son of Drena De Niro , Robert De Niros adopted daughter.

Its just a shock, Robert De Niro said. [I] never thought it would happen.

And I just then started thinking about all the things I could have, should have done maybe with him, he continued. I dont know if that wouldve made a difference. And so thats always playing through my mind. It shouldnt have happened.