Like nearly everything connected to the JFK assassination, the location where officer J. D. Tippit was killed by Lee Harvey Oswald has an historical marker and an “X” painted on the street today (though judging from the bloodstains in the B&W photos, not sure if “X” really does “mark the spot” – seems too close to the curb IMHO).
RIP J.D. – we are forever in your debt.