How exactly did Henry die in the Time Traveler's Wife?

I know that the brother shot him. But on that day he called out to clare and when she came out she saw him with her father and brother. Did they shoot him because he was amputated and could not run? Did they even realize they shot him? When the brother and father meet him during that christmas with Clare, they mention something about

"what an uncanny resemblance" So they obviously had some sort of interaction, what was it exactly. This part seriously confused me and I believe it was one of the most important parts in the book since this was basically the climax. I hate not knowing exactly took place.