How do I say “He already went to do X for me”, implying he is still in the process of X, not finished?

Question

The other day at some festival a few japanese friends asked me something to the effect of

アイスを買ってくるけど、行く？

But I had already asked a friend, who had not yet returned, to get some for me. So I said

ジェームズがもう買って来てくれたので大丈夫。

What I intended to say in English was "No thanks, James already went to get me some." But it seems that the japanese version of that statement could have multiple meanings.

How do I differentiate between "He already bought it for me (and has completed this process)" and　"He has already gone to buy it for me (and has not yet completed this action)"?

(もう買ってきてくれている could be a possibility, but for some reason doesn't sound correct to me. )

Answer 1

ジェームズがもう買って来てくれたので大丈夫/もう買ってきてくれている would mean "James already bought it for me (and now I have it)". I'd say

ジェームズが(今)買いに行ってくれてるから大丈夫

or

(今)ジェームズが買いに行ってるから大丈夫。

Answer 2

Your sentence:

ジェームズがもう買って来てくれたので大丈夫。

Implies that he went to buy and also came back. This is known because of the two verbs - 買って + 来て.

If you want to say that he went to go get ice cream for you, then how about saying something like:

ジェームズがもう買いに行ってくれてるので大丈夫。

This way it states that he went to go buy it (but hasn't come back).

EDIT: I forgot to mention that 「くれた」 in the first is past tense because you already got the item supposedly. For the second, you haven't received it yet, but you are expecting to.

Answer 3

Notice that the main verb is different for your two cases:

1. James already went to buy me ice-cream

2. James bought me ice-cream

Simplifying:

1. James went ~

2. James bought ~

For 1. you would want 行く to be the main verb, and for 2. you would use 買う:

1. 買いに行ってくれている　- (went in order to buy)
2. 買ってくれている - (bought)