Hackman did *NOT have photos of the girls dead
*SPOILERS
Many posters here have repeated that the police found photos of the girls' dead bodies in Henry's possession.
Not at all true. If you watch the movie, Henry has a few photos of ONE of the dead girls when she was very much alive.
But Henry was a photographer and has a hillion-jillion other pictures. He even has his own dark room in his home, so it is not unlikely that he would have such a picture.
The REAL killer at the end has photos of BOTH girls after they are killed, sealing his identity as the killer..