^^^The latter.
From the November 3, 1966 Final Draft. After Kirk tells Lang and O'Herlilhy and (it's Molton in the script, I think it was Kelowitz in the aired episode) to look for survivors, etc. we have the following, which I will not try to reproduce in standard script format:
The others leave as per their instructions. O'Herlihy bends to examine some of the wreckage as Spock and Kirk study the tricorder.
SPOCK: The human population of the Cestus Three outpost is listed as five hundred twelve. I get readings of less than half a dozen... widely scattered.
KIRK: The others are all dead?
SPOCK: They do not register.
O'HERLIHY: Captain!
O'Herlihy indicates some of the wreckage.
O'HERLIHY: Some of this was caused by something like phasers. But this... some kind of an internal explosion.
SPOCK: CAPTAIN!... Impulses from that direction. Very weak. Possibly a survivor.
KIRK: Come on, Bones.
The four of them move in the direction indicated by Spock, Kirk leading; all phasers ready.
TRUCKING SHOT THROUGH RUBBLE
KIRK: Who sent the message inviting us down here, Spock?
SPOCK: The answer to that will solve many mysteries, Captain. Obviously, someone who wanted you and your top tactical aides on the surface.
KIRK: Why?
McCOY (reacting off): Captain... over there.
End of script excerpt.
So I imagine it was some of the above dialogue. In this draft, the teaser does not end until after Kirk calls the Enterprise, tells Sulu to keep the screens up, etc.. I think I detail that in my review of the script, located by following the link below.
Sir Rhosis