Two packages mailed from China, destined for an address in Milwaukee, were intercepted in February by federal agents in Alaska and Tennessee, according to court records.

Inside, investigators found parts that turn a Glock semi-automatic handgun into an illegal machine gun, meaning it will fire continuously with a single trigger pull.

Last week, prosecutors charged a 23-year-old Milwaukee man, Curtis Fisher Jr., with illegal possession of a machine gun, conspiracy and having a firearm as an unlawful user of a controlled substance.

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A complaint in the case offers an insight into how authorities try to stem, or even slow, the flow of parts that turn deadly handguns into even deadlier machine guns.

Export of such parts from China is illegal. Both intercepted packages were addressed to Luckyy Rich, at an address on North 25th Street in Milwaukee. Investigators traced the address and a phone number associated with the orders to Fisher.

They also learned three prior packages were delivered in January and were not intercepted. During a search of Fisher's home in March, agents found two guns and numerous rounds of ammunition and a subject willing to talk.

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According to the complaint, Fisher told agents "everybody who is in the streets of Milwaukee is looking to purchase Glock auto-sears to install on their firearms." Auto-sear refers to the device that converts a semi-automatic to a fully-automatic gun.

Fisher further told agents in December, his half-brother explained he had found a way they could purchase the parts, via Alibaba, a Chinese e-commerce site. Once Fisher started an account, he said someone selling the auto-sears, "Doris," had him communicate via WhatsApp.

Fisher said his first order was for two auto-sears, and a second was for five of the devices. He said he turned over each delivery to his half-brother.

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He said he used tax refund money to make the third order, for $275. When the packages didn't arrive, Fisher told agents his half-brother suspected him of keeping the auto-sears to sell on his own.

Fisher told the agents he's never fired a gun fitted with an auto-sear but was able to describe how they work.

Fisher said he thought the search warrant was related to a recent shooting he had been involved in. He explained his friend was coming out of a corner store at North 26th and Nash streets and said he'd had a run-in with another man.

When that man exited and raised a gun at their car, Fisher said he fired about a half dozen rounds at the other man, using the Glock handgun agents recovered in his apartment. He did not report the incident to police, Fisher said.

Fisher was arrested Oct. 7, made an initial court appearance and was released on conditions, including that he not possess any guns or gun parts.

Contact Bruce Vielmetti at (414) 224-2187 or bvielmetti@jrn.com. Follow him on Twitter at @ProofHearsay.