Crowley rushes into the burning building to save his friend - to save Aziraphale.
- Debatable - they're both immortals, and Crowley is in a panic, on the run from the Dukes of Hell, and is clearly rushing to find Aziraphale due to not knowing who else to turn to. However, Aziraphale dying at this point would mean that he's unlikely to acquire a new body anytime soon which, seeing as the world is about to end, means they'll likely never see each other again. So while there's no reason for Crowley to have been concerned for Aziraphale's wellbeing, it is heartwarming how desperate he is to stay together with him.
- Even without any of that being taken into consideration at all, it's clearly stated — with emphasis — that Crowley was looking for help. When a war between Heaven and Hell was on the verge of breaking out, with demons and angels about to make the leap from 'casual enemies' back to 'full-scale soldiers in active battle to the death', Crowley's instant response was to find Aziraphale — no, not to finally kill his Enemy of six thousand years, but rather to find an ally. It did not even occur to Crowley that their Arrangement might in any way be changed or rendered null and void by the looming war between their respective sides. True Companions!
- And relatedly, that when Aziraphale figures out where the Apocalypse will begin, his first instinct is to call Crowley.
He ought to call Heaven. He wanted to call Crowley.