Public shootings have become increasingly common over the past few years. Over 250,000 people die every year as a result of shootings worldwide. In all existing solutions, the authorities are only alerted after the attacker is spotted by civilians, after the incident—at which point it may be too late to save lives. Assurance is a proactive, effective, and affordable mass-shooting prevention system designed to work with existing security systems. It works by scanning the aggregate input from security camera feeds for firearms and alerts all parties it needs to alert as soon as a firearm is detected. The system is fully extensible and is able to run on low-cost hardware to make it accessible for everyone, regardless of their socio-economic background.