He done this because he was threatened by the police officer.
Done is used as the past simple of the verb do. I do not know why an Asian writer would use this construction. Do you have a link to the book, or can you remember the book's name?
Done is the past simple of do in the dialect of English spoken throughout the southern United States. Not all people in this area always use done in this way. Because people can use both dialect English and standard English. For example, I am from the American South, and I can speak this dialect when I want to sound like I am from the American South.
However, some people only speak dialect English. An unfortunate occurence is that such people are seen as speaking an "inferior" or, as you put it, a "weird" form of English, because of the way their dialect differs from standard English. And such people can be seen as "ignorant," meaning not only uneducated but stupid.
Famous authors of the South who wrote using a Southern dialect include
Katherine Anne Porter
James Lee Burke
My suggestion for English learners is to first learn standard English. Dialects contain not only grammatical constructions that differ from 'standard English' but also employ different words for things. And of course pronunciation is a huge identifying factor.
Wikipedia has an article about this dialect at this link.
The dialects of American English commonly known collectively in the United States as Southern are spoken throughout the Southern United States, from the southern extremities of Ohio, Maryland, and Delaware, as well as most of West Virginia and Kentucky to the Gulf Coast, and from the Atlantic coast to most of Texas and Oklahoma, and the far eastern section of New Mexico. The Southern dialects make up the largest accent group in the United States.
In this dialect done can be used in the following ways:
1) as the past simple of do -- this is how the word done is used in your sentence.
I done what you told me.
2) as an auxillary verb before a main verb to mean the past tense:
I done told you to stay away from Boo Radley.
I done asked (or axed) the man what time breakfast was.
These two uses can naturally be combined:
I done done it.