The arrest took place in Salasar, Rajasthan, where Kumar was seized during a coordinated operation by Punjab and Rajasthan police on Wednesday.
Sources on Wednesday said the shopkeeper fled after shooting Parvinder Singh Jhota, an anti‑drug activist, during a Facebook Live session on Tuesday.
Jhota had been warning locals about illegal drug sales at chemist shops for years, and his 24,000‑strong Facebook following grew after a July 12 incident that saw him clash with a shopkeeper.
The police also apprehended an aide who allegedly helped Kumar escape, and authorities are now investigating whether other drug vendors may have been involved.
Kumar faces charges of murder and related offenses, and the case will be heard by the Rajasthan court before being transferred to Punjab's jurisdiction.
The incident has reignited calls for stricter regulation of medical stores in Punjab, with local councilors demanding an audit of all pharmacies.