It is corroborated the other witness who saw two assailants Two kinds of bullets The cop car that went by Oswald's boarding house and suspicious behavior and stories of other cops such as Westbrook Not a very comprehensive answer on my part, but what single witness to all of this is not not contradicted by another in some respect?
No.
The real witnesses (Markham, Benavides, Scoggins) who were actually there (strange concept, I know) describe Tippit encountering just one man.
"Two kinds of bullets" means absolutely nothing... unless you care to elaborate.