Why does the Mariner shoot the albatross-Does he have any reason or is it just pointless sin?

The A letter from Margaret 

Rime of the Ancient Mariner (179798) is a ballad by Samuel Taylor Coleridge.
version that pairs the ballad with the French illustrator Gustave Doré‘s amazing illustrations (from 1870), which help you follow the story a lot better.
Questions to help guide you through understanding the reading:
Why does the Mariner shoot the albatross? Does he have any reason or is it just pointless sin?
What very famous religious story does the Rime allegorize?
What is the environmental or animal rights lesson in this poem?
Why do all the other sailors die?
What connection do you see between these lines and Walton’s letters?:
Alone, alone, all, all alone,
Alone on a wide wide sea
And never a saint took pity on
Soul in agony.
(2336)
How does the mariner break the curse of the albatross?
What happens to the dead men after the curse is broken?
What is the role of the hermit in the poem?
What does the wedding guest do at the end? Why is he sad the next day?