Federal prosecutors charged a US Navy reservist earlier this month with illegally manufacturing military-grade weapons in his Maryland home, including AR-15 and AK-47 assault rifles, according to newly unsealed court documents obtained by Quartz.

Investigators said they also found computer-controlled milling equipment and a hydraulic press, which are used to make weapons, as well as multiple handguns, rifles in various states of completion, thousands of rounds of ammunition, and instruction manuals for building improvised explosive devices, or IEDs.

It’s unclear what the reservist, 38-year-old Tamufor Nchumuluh St. Michael, wanted with all these weapons, though according to the documents he may have intended to sell them. St. Michael joined the Navy Reserve in 2008, the filings say. St. Michael is now assigned to the Naval Operational Support Center at Joint Base Andrews, the same Maryland facility where Air Force One is based.

Finding a private cache of weapons like this is worrying for any number of reasons, not least among them is that they could be used in a mass shooting. There have been some 280 mass shootings so far in 2019, killing 296 people and injuring another 1,059. The latest occurred Sunday, when a gunman opened fire at the Gilroy Garlic Festival in California, killing three people and injuring another 20. The shooter used an AK-47-style assault rifle, which he legally purchased in Nevada on July 9.

While some states have passed their own gun control legislation, federal gun control laws have stalled in the Republican-controlled Senate. Senators have so far refused to vote on a bill approved by the House in late February. Among other things, the House bill would force private sellers to obtain a federal license.

All of the guns and parts purchased by St. Michael were obtained lawfully. He even used his military ID card to get a discount in at least one transaction. The feds say they have evidence of St. Michael making at least 133 purchases from gun dealers around the US in the last year, which came from data provided by the sellers themselves.

The number of guns found, “coupled with the manufacturing equipment and several firearms in various states of assembly located within the residence, indicate that St. Michael is engaged in the unlawful manufacturing of firearms without a license,” according to case filings. While St. Michael is a state-licensed firearms collector, prosecutors say this does not authorize him to “act as a firearms dealer.”

Joseph Giacalone, a former New York Police Department detective and unit commander who now teaches at the John Jay College of Criminal Justice in New York City, said the arrest may have saved lives.

“It looks like all of the checks and balances worked this time and may have headed off a mass shooting,” Giacalone told Quartz. “I’m glad to see sellers making appropriate notifications and I hope that there is no backlash against them for doing the right thing.”

St. Michael’s attorney did not respond to a request for comment. The Department of Defense referred Quartz to the Navy. A Navy spokesman declined to comment and referred Quartz to the Department of Justice, which declined to comment while the case is still ongoing.

St. Michael, who came to the US as a refugee, has never been in serious trouble before, according to public records. In 2011, the year he became a US citizen, St. Michael filed an immigration-related lawsuit against Department of Homeland Security secretary Janet Napolitano, attorney general Eric Holder, Maryland US attorney Rod Rosenstein, and officials with US Immigration and Citizenship Services. The case was dismissed four months later after St. Michael failed to serve papers to those named in the lawsuit. Additional information is not available, as the documents remain sealed.

St. Michael is free on bail pending his next court date. He was ordered to surrender his passport and is not allowed to leave Maryland without permission.

“I’d like to say I’m shocked by these developments, but I’m not,” Giacalone said. “The real question is, how many more of these guys are out there?”

The charges come less than three weeks after two US Marines were arrested for sneaking undocumented immigrants into the country, a story first reported by Quartz. Since then, at least 14 other Marines have been ensnared for participating in what authorities are now investigating as a possible human smuggling ring.