First off-- Nima is a person of interest. It doesn't mean he's guilty of anything. Even if they were in a car together, argued and Bob left the car and walked it doesn't mean Nima killed the man.
I assume (and hope) the police have more solid evidence like a fingerprint on that knife or Nima's own blood/DNA at the scene or on the knife as is common with stabbings.
You cease to be "a person of interest" and become the suspect right about when the cops drive across the Bay Bridge to pick you up and bring you to jail.
I assume (and hope) the police have more solid evidence like a fingerprint on that knife or Nima's own blood/DNA at the scene or on the knife as is common with stabbings.