This is why you never talk to LEO's without a lawyer. If you have the time I highly recommend watching this video:
I imagine I can become a suspect from a witness, if I make a mistake which is seen as a lie.
You hear a loud bang and see a car speeding away. Later on, from your window, you see that police have arrived and are investigating. Would you go and offer the info, what car, maybe number, at what hour.
Or lawyer up first, because where I live, finding a lawyer is not a common thing to do.