I agree with vengeful. The woman didn't know that someone had been killed. Roads are cordoned off all the time, lights could have been out, stolen car dumped by joyriders, dodgy vehicle clocking police and chucking something from window, burst water main, gas leak, there are a million reasons.
It is very sad about the old lady but I think you were BU to snap at someone who was having a general whinge and had no way of knowing what had actually happened.