It is never made clear whether the incident outside the jewelry shop near the end is a deliberate murder or simply an unfortunate accident. If it is supposed to be an accident, it makes no sense that the driver of the car doesn't stop, and that Laurence appears to be fine with just letting him get away. But if it is supposed to be a murder connected to the other murders, Laurence makes no reference to it whatsoever when he explains his solution to the other crimes and takes the killer into custody at the end.