What to do a false case filed against my friend

My friend is falsely framed in the case of accident. What actually happened: My friend(lets say f1) and his friend(lets say f2), they were coming from a function at midnight around 1 am and f1 was driving a car and some heavy vehicle hit their car and car crossed from divider to opposite lane. F2 died in this accident and F1 is still recovering. Now on that same night another dead body(3rd person lets say P1) found at the spot of accident and P1’s family claiming that P1 died due to F1’s car. But there is no cctv and no one knows how did this happen. What is framing by police: Initially the section was 304A in this case but by an influence from some X person this section has been converted from 304A to 304 section. And police is mentioning that the driver F1 was drunk and was driving @160/hr speed. But they don’t have any blood reports and even we don’t have any blood reports. My concern: What should we do if this case if police come with arrest warrant and how should we deal