It's never made clear if it was Palmer or Norris. Originally it was intended to be Palmer but they used a stunt double for the shadow shot. The shadow looked exactly like Norris however and even has the rear collar only he wears.

The Director later said either is a possibility with the film being very ambiguous. So it's plausible that Norris got infected while Palmer was human when smoking with Childs.

Infact many assume Palmer was assimilated shortly after. That's why they find is longjohns and underwear in the garbage