'And that's when it happened. And I don't even remember - that's the hellish thing' - he can barely bring himself to talk
'And' - repeated=shows how he wants to get it out of his brain and clear his conscious by admitting what he's done.
'it' - vague, ambiguous, dissociates him from the situation
'I don't even remember' - shows how it didn't mean anything to Eric, but it meant everything to Eva as it cost her her life
'hellish' - religious connotations of hell - extremely religious in the Edwardian Era