In the first public accounting of its kind in decades, an Associated Press investigation has found that at least 1,900 U.S. military firearms were lost or stolen during the 2010s, with some resurfacing in violent crimes. And that's certainly an undercount.

Government records covering the Army, Marine Corps, Navy and Air Force show pistols, machine guns, shotguns and automatic assault rifles have vanished from armories, supply warehouses, Navy warships and elsewhere. These weapons of war disappeared because of security failures that, until now, have not been publicly reported, including sleeping troops and a surveillance system that didn't record.

In one case, authorities linked an Army pistol stolen from Fort Bragg, North Carolina, to four shootings in New York before it was recovered. Another stolen Army pistol was used in a Boston street robbery.

Weapon theft or loss spanned the military's global footprint. In Afghanistan, someone cut the padlock on an Army container and stole 65 Beretta M9s -- the same type of gun recovered in New York. The war zone theft went undetected for weeks, when empty pistol boxes were discovered in the compound. The weapons were not recovered.

While AP's focus was firearms, military explosives also have been lost or stolen, including armor-piercing grenades that ended up in an Atlanta backyard. In that incident and many others, military investigators closed the case without finding the person responsible.

The Pentagon used to share annual updates about stolen weapons with Congress, but that requirement ended years ago and public accountability has slipped. The Army and the Air Force couldn't readily tell AP how many weapons were lost or stolen from 2010 through 2019.

The green, metal box was stuffed inside a bright pink pillowcase and stashed in the bushes behind Christopher Zachery’s house. He hauled it out for a better look.

Stenciled on the box: “Cartridges for weapons.” Inside were 30 armor-piercing grenades.

“I was scared,” said Zachery, who runs a construction company. And confused. How did these high-powered explosives end up in his southwest Atlanta backyard? Where did they come from?

Investigators determined the waylaid grenades were last seen eight month prior on an ammunition train that rolled out from Florida. Someone had stolen them somewhere on the rails to Pennsylvania, another example in an Associated Press investigation that shows how the military’s vast supply chain is susceptible to theft.

Marines call the squat, 40mm rounds that appeared in Zachery’s yard on that sunny morning in February 2018 “40 mike-mikes.” They’re linked together to feed into an MK 19 launcher, a weapon that is like a machinegun for grenades, able every second to shoot one nearly a mile.

Awaiting the bomb unit, Atlanta police evacuated five houses in both directions, as well as neighbors across the street. The rounds can penetrate three inches of steel and have a kill radius of nearly 50 feet.

The canister began its journey at Blount Island, a U.S. Marine Corps depot in Jacksonville, Florida. Six flatbed rail cars hauled 18 large storage containers known as conex boxes, each with an orange sign warning “Explosives” on its side. On car DODX48916, inside container USMC007574-6, canisters of the 40 mm rounds were stacked like soldiers in bunks.

The train’s circuitous route passed through Atlanta twice before it arrived 17 days later at Letterkenny Army Depot in central Pennsylvania. There, a worker unpacking the container discovered the theft.

Where, when, who, how -- investigators were at a loss.

A series of security failures covered any tracks the thief left.

Armed guards who accompanied the shipment reported nothing. When the train reached Letterkenny, it was shuttled for the night to Rail Yard 1, an unsecured staging area outside the installation with no surveillance.

Upon arrival, workers didn’t verify whether anti-theft seals on each container were intact. An inspector didn’t check the seals the next day either, later saying it was because he couldn’t see them.

Yet another day passed before workers noticed the broken seals. The first laborer who saw the severed wooden framing used to hold pallets of canisters together thought it broke in transit. Then he noticed a metal strap that holds each canister snugly to the wood also was cut, and one box was gone.

Military investigators would conclude that no one checked the seals in the weeks after the train departed Blount Island.

Workers unpacked the entire container to see whether anything else was stolen, disposing of debris. For investigators, that meant the crime scene near loading dock X-11-G was contaminated beyond repair.

The Pentagon’s inspector general wrote that the disappearing grenades “further emphasized the lack of proper security for rail shipments” of military arms, explosives and ammunition.