At least Getty isn’t claiming ownership. Yet...
Maybe - but they do have some of his works in their museum. Suspect the Mail added the copywrite notation to keep themselves on the 'right' side of the pernicious US laws!
Found this one at another site, Masters of Photography. He did a lot of work on the Civil War:
Timothy O'Sullivan
A Harvest of Death,
Gettysburg, Pennsylvania
July, 1863