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As one of the vital topics in intelligent surveillance, weakly supervised online video anomaly detection (WS-OVAD) aims to identify the ongoing anomalous events moment-to-moment in streaming videos, trained with only video-level annotations. Previous studies tended to utilize a unified single-stage framework, which struggled to simultaneously address the issues of online constraints and weakly supervised settings. To solve this dilemma, in this paper, we propose a two-stage-based framework, namely “decouple and resolve” (DAR), which consists of two modules, i.e., temporal proposal producer (TPP) and online anomaly localizer (OAL). With the supervision of video-level binary labels, the TPP module targets fully exploiting hierarchical temporal relations among snippets for generating precise snippet-level pseudo-labels. Then, given fine-grained supervisory signals produced by TPP, the Transformer-based …