Harry Potter Nerds! Why did Voldemort kill James and Lily Potter?

I have no idea but I have read the whole series more than once. I think Wormtail gave away information to Voldemort that Lily and James had a son and they (meaning Voldemort and Wormtail) wanted to blame Sirius Black(the Godfather of Harry) for killing them (Lily and James) but don't forget that Voldemort did kill innocent people for no reason