Heimgartner (#8 R&J Batteries ZB Commodore), who started from Row 6, was unable to avoid the stricken Ford and ploughed into the back of it.
Nick Percat (#2 Mobil 1 NTI ZB Commodore) also sustained damage when Randle's car cannoned into the side of his as he sped through the scene on drivers' left.
Heimgartner and Randle both walked walk away from the wrecks, although the former looked particularly sore/winded, while Percat came to a halt at Turn 1.
The session is set to eventually go to a full restart, with Cameron Waters on pole position in one of the surviving Tickford Mustangs.
Up to 22 laps will be run, although time-certainty of 13:33 local time/14:03 AEST (plus one lap) may prevent the contest from reaching that distance.
Meanwhile, Red Bull Ampol Racing has fitted a new front bar to Shane van Gisbergen's #97 ZB Commodore after he incurred damage in a separate incident further up.
Update 13:16 AEST
The field has headed back onto the race track.
Update 13:20 AEST
Update 13:23 AEST
Time-certainty now 13:30 local time plus one lap.
Update 13:29 AEST
Race has restarted.