！。
You're destroying evidence — what the heck?! Normally you'd call the cops, right?!
Literal
Evidence-destruction how-do-you-[emphatic-のよ]?! Normally [topic-は] police [to-に] contact do [nominalizer-もの] [right-でしょっ].
どーすんのよ stacks several contractions: どう → どー (vowel lengthening), する → す (before ん), のよ (emphatic 'what are you doing?'). The stacking is characteristic of brash, emphatic spoken Japanese. するもんでしょ uses もん (contraction of もの) as a generalizing nominalizer: 'it's the kind of thing [one does],' often with an implied 'normally.' The final small っ on でしょっ adds sharp finality to the utterance, imitating a clipped/angry tone.