Other mistake: During the big chase scene, a car hits a camera right after it passes a blue '68 GTO.
Other mistake: Just before the Charger crashes, a tow bar connecting both vehicles is visible on the Mustang's front bumper.
Other mistake: When we get a front shot of the two cars jumping the hills, watch when the Mustang lands on all four wheels. It gives out a tremendous amount of smoke and steam from underneath. (Slow it down on DVD for the full effect.) This is because the car landed too heavily and shattered the sump (oil pan). The other Mustang had to be used while the mechanics repaired the damage.
Answer: Notice: Aprea is credited as "Killer", not "The Killer." I think this confuses reviewers, as they assume he must be one of the hit men. However, the hit men are credited as "Phil" (Bill Hickman) and "Mike" (Paul Genge). Genge is much older than Aprea and Aprea does not look like the grey-haired hit man, as another contributor has pointed out already. There is no other killer in the plot. Perhaps Aprea's scenes were cut.