I agree that we don't have the details of the incident. We don't know exactly HOW the guy responded to the officer's attempt to identify himself as LE.

Was it:
"Oh shit, the cops! You'll never take me alive!" *pulls knife*
or
"I don't believe you, where's your ID?" To which the cop replies, "I don't have my badge on me at the moment."
"Then get away from my car!" *pulls knife*

And then the suspect would have just assumed he was being attacked by any other person.