JERSEY CITY — Five months after losing his daughter to an overdose, John Cramsey, a gun range owner from Pennsylvania, embarked on a crusade against drugs.

His cause steered him last year toward a drug den in Brooklyn to try to rescue a 16-year-old girl from the same fate as his daughter.

But Mr. Cramsey’s impromptu mission, in a truck filled with firearms and emblazoned with decals celebrating gun culture, was cut short.

The police arrested Mr. Cramsey, 52, and two others on the New Jersey side of the Holland Tunnel on June 21, 2016, after finding five pistols, an AR-15 assault rifle, a 12-gauge shotgun and a small amount of marijuana in Mr. Cramsey’s black Dodge.