Question

If you don't come out we will break open the door the police threatened",
begin the police threatened them that

Answer 1

The given sentence can be written as specified in the following manner:

The police threatened them that if they did not come out they would break open the door.

It was direct speech sentence that was to be converted into indirect speech. It was a simple statement. So, we applied the tense change and pronoun change rules that we usually apply while converting the direct speech into indirect speech.

Answer 2

the police threatned them that if they did not come out they would break open the door