had car weighed down with 5 boxes of tiles and heard a loud snap kind of noise
Either your shocks or rear springs caused the snap. Does it sit or ride different? Some times with no weight and you go over a rough spot, R X R tracks or pot holes a spring may pop out of the cup it sits in and that extra weight may have snapped it back into the cup. Check the shocks and springs for any visible damage, broken spring or a leak in the shocks.
For some reason this site seems to double post answers so I deleted my dual second answer.
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