Пытался for a one-time action

Question

Why is the past tense of the imperfective verb пытаться used in this context?

Говорят, он пытался убить сына Поттеров, Гарри. Но – не смог.

I would expect попытался to be more appropriate here since, whoever he is, tried to kill Гарри once, not several times in the past or something like this such as a past habit.

Wider context:

– Говорят, – не сдавалась профессор Макгонаголл, – что прошлой ночью Вольдеморт объявился в Годриковой лощине. Пришел за Поттерами. И по слухам, Лили и Джеймс Поттеры… Лили и Джеймс… погибли. Думбльдор склонил голову. Профессор Макгонаголл охнула. – Лили и Джеймс… не могу поверить… не хотела верить… Как же так, Альбус… Думбльдор похлопал ее по плечу. – Ну-ну… ничего… – мрачно произнес он. Профессор Макгонаголл продолжала, и голос ее дрожал: – Это еще не все. Говорят, он пытался убить сына Поттеров, Гарри. Но – не смог. Не сумел убить маленького мальчика. Никто не знает, как и почему, но, говорят, когда ему не удалось убить Гарри, он вдруг словно бы потерял силу – и исчез.

Answer 1

"Пытаться" and "попытыться", apart from continuous vs one-time effort, has another difference in Russian language.

"Пытаться" is associated with an all-out, earnest effort to do something.

"Попытыться" implies that either the effort was inadequate, or the chance of success was small to begin with.

"Он пытался открыть дверь" / "He tried to get the door open" - He did everything that he could at the moment (pushing hard, trying keys, maybe even a crowbar or a ram) to get the door open.

"Он попытался открыть дверь" / "He tried to open the door" - His made an initial, small-scale effort (just the door handle, or maybe one key, but without any jiggling or such) to open the door.

In both cases it is implied that the effort was unsuccessful. However, in case of "попытался", there may be an unexpected success. "Он попытался потянуть дверную ручку на себя, и к его удивлению, дверь открылась" / "He tried to pull the door handle, and, much to his surprise, the door did open".

Answer 2

The thing is, убить is really a one-time action, so a perfective verb is used, but пытаться убить is far from being one-time, it took some time, there was a kind of struggle with what prevented the attempt, that's a reason why the verb is imperfective.

It is a mistake to think that the Russian verb aspect has a 1:1 correlation with some categories of the English verb. A story about past events is typically told in Past Simple in English, which is both non-Continuous and non-Perfect, while in Russian such stories are usually told in the Past using perfective verbs, e. g. вырос, женился, построил дом, завёл жену и детей, умер, but the story traditionally begins with жил-был which is imperfective. Why imperfective? Although the character existed and lived only once and his life is over, it lasted for some time. Actions (or states) that last for some time are Usually rendered in English by Perfect Continuous tenses (has/had been doing), and it is this Continuous element that is often present in the Russian imperfective verbs, its presence is never to be forgotten.

The Russian Past tense of imperfective verbs can have three main meanings:

1. a multiple, repeated action which was performed usually, regularly, often, several times, always, corresponds to the English Past Simple/Indefinite Tense (worked, played, lived):
   Каждое утро он вставал до рассвета.
2. an action which was happening at a particular moment in the past, corresponds to the English Past Continuous Tense (was/were doing):
   Вчера в 5 часов вечера он сидел в кафе и пил кофе.
3. an action that took some time, corresponds to the English Past Perfect Continuous Tense (had been doing):
   Он два часа пытался решить эту задачу, но в конце-концов сдался.

Your first guess was meaning #1, but there are 2 more meanings to be considered. The attempt to kill Harry Potter could take some time, and obviously there was a witness who spread the word about the attempt, so the attempt was possibly going on when the witness saw it.

Answer 3

Говорят, он попытался убить сына Поттеров, Гарри. Но — не смог.

It means "he has tried to kill Harry".

This is a pronounced one-time action which has turned the character from a person who had never tried to kill Harry to a person who had (state transition).

It focuses on that one time and its consequences.

Говорят, он пытался убить сына Поттеров, Гарри. Но — не смог.

This is a description of the character's attempt (or possibly multiple attempts) to kill Harry.

This means "he tried" or "he was trying" and describes a state: at some point of his life, the character engaged in activity of killing Harry and was carrying it out for some time or several times, to no avail.

It focuses on the activity itself, not how the things were before and after.

Update:

Within this context, you can use either aspect.

If I encountered this during my normal course of reading, I probably wouldn't even have registered which aspect did the author use.

As I said, there are some minor differences (he might or might not have tried to kill Harry multiple times with the imperfective, or it might have taken him some noticeable time), but they do not change the meaning of the text in any significant way.