He killed his own wife and kids and fled to mexico where he passed himself off as a reporter from the New York Times(?) He chose to pose under the name of a real reporter. Not only that but he lived rather well and began a relationship with a female photographer who thought she had really gotten lucky to be working with this well-known reporter. Meanwhile the real reporter had gotten sacked.
Somehow the whole thing came out and he ended up in prison. The now-unemployed reporter whose identity he had stolen interviewed him and wrote a book about him.
That’s all I remember.