The man who shot and killed Joe McKnight tracked another motorist into a gas station -- attacked him -- and then vowed more violence during a 2006 incident ... this according to the police report obtained by TMZ Sports.
Ronald Gasser -- who has admitted to shooting McKnight last week -- was previously named a suspect during an incident on Feb. 20, 2006.
The person who filed the report says Gasser was driving a red Isuzu in Jefferson Parish, LA -- the same area where McKnight was shot -- when Gasser cut him off .