It might have been something like Millimeter-Wave / Microwave Weapons (e.g., Active Denial System) - see this: https://www.gao.gov/products/gao-23-106717 https:

It might have been something like Millimeter-Wave / Microwave Weapons (e.g., Active Denial System) - see this: https://www.gao.gov/products/gao-23-106717 https://www.gao.gov/products/gao-23-106717 .