Hello, everyone.

Today I have a question as to the usage of 'be surprised at + -ing' and 'be surprised + to-infinitive'.

One of the students at my school wrote:

1. My mother was surprised at hearing the news.

(I'm pretty sure that the student used the -ing form (a gerund) because of the preposition 'at'.)

I believe it is grammatically correct, but I think it would be more natural to say:

2. My mother was surprised to hear the news.

or simply

3. My mother was surprised at the news.

Is the sentence #1 written by the student acceptable/natural?

Thank you.