Translation:The burglars are in the house, from which even the policemen run away.
where is the idea of "even" in this sentence. and why is "is" not too, or also?
is can mean "even" in sentences like this. That meaning is clearer if you use it in conjunction with még, as in ...még a rendőrök is elfutnak.
It's possible to translate this sentence with "too" or "also", but it's unlikely to be the right meaning. There's nobody else in the sentence who is running away from the house, so "the policemen also" doesn't really fit well.
However, there have been incredibly many example sentences that included an "is" in ways that it referred to something that must have happened before/outside the example sentence.