Translation:You are policemen, are you hurrying here too?
Because in the Hungarian sentence the two clauses are independent. They could function as separate sentences as well: "Rendőrök vagytok. Idesiettek ti is?"
Your sentence would be better translated as "Rendőrök vagytok, akik idesietnek?" where a subordinate clause is used to fill the role of the participle "hurrying".
In written, it is decided by the question mark / period. In spoken, it is decided by the intonation. Indicative (.) mood is marked with descending intonation. Interrogative (?) mood is marked with either "ascending-but-ending-with-sudden-fall" intonation (used when there is no question word) or "descending-but-ending-with-sudden-rise" (used when there is a question word)
eg1. idesiettek ti is? --> it is ascending until ti, but is is toned low.
eg2. miért siettek ide? --> it is descending until the i in ide, but de is toned high.