They were hanging out late last Tuesday when members had to scramble for cover.

Four people were injured when a gunman leaned out of a passing SUV and sprayed the area with what sounded like an automatic weapon — a theory confirmed by witness testimonies and the ShotSpotter.

The incident last Tuesday extended a string of shootings involving ordinary handguns and rifles that were modified into fully automatic weapons capable of firing up to 1,200 rounds per minute.

The conversion process involves illegal devices commonly referred to as "Glock switches" or "auto-sears," which are readily available to buy on the internet or can be made on 3-D printers. Police and crime prevention workers say that these converted guns are showing up at more and more crime scenes.

Quantrell Urman, founder of the street outreach group Turf Politics, said that not a night goes by that he doesn't hear automatic gunfire while making his rounds.

"They're out there a lot," he said. "They're everywhere."

The constant threat of gunfire also is making it harder to recruit people for the work of interrupting the cycles of violence that plague some parts of the city, he said.

"It deters a lot of people from going out there. A lot of those guys don't have life insurance, they don't have medical and we can't carry weapons," he said. "So we're in a lose-lose situation that do it."

Although it's unclear how many auto-sears are on city streets, authorities have been tracking incidents involving such devices and investigating those suspected of wielding them, said Jeffrey Reed, the assistant special agent in charge of the Bureau of Alcohol, Tobacco, Firearms and Explosives' St. Paul field office.

While regular semiautomatic guns fire one round for each time a trigger is pulled, an automatic gun will shoot continuously until the trigger is released. Conversion devices like auto-sears can quickly and easily be fitted onto a Glock handgun by removing the polymer slide cover plate, a process that requires little technical expertise.

"It can be done in about 60 seconds," Reed said.

ATF spokeswoman Ashlee Sherrill said that in response to rising gun violence, the agency has embedded some of its agents with Minneapolis police's homicide and gun investigations units.

Many shooters also are outfitting their guns with extended magazines that can hold more bullets.

According to police statistics, the city's ShotSpotter network has recorded 78 automatic gunfire activations of 935 total rounds, compared to only five such activations of 42 rounds at this time last year. The increased firepower comes as the city is closing in on last year's record of 551 gunshot victims. Minneapolis, like many other cities, saw shootings and homicides soar in 2020, a trend that has continued in the first half of this year.

Several recent shootings across Minneapolis underscore the devices' prevalence.

In August, ShotSpotter detected 27 rounds of automatic gunfire in a shooting at Winner Gas that left one man dead. One round also grazed the ankle of a woman who was pumping gas while her young children sat in her car.

That same month, police said a modified fully automatic pistol was used in a shootout on a busy Uptown street in which more than 100 shots were fired and seven people were wounded. And earlier this year, two men were injured when automatic gunfire broke out during a house party near the corner of Penn and W. Broadway avenues. One of the victims was in a wheelchair, paralyzed from the waist down from injuries suffered in another shooting seven years prior.

The increase in such incidents coincides with other worrying trends, officials say, including the growing number of shootings with fully automatic rifles and so-called "ghost guns," which can be assembled at home from parts bought on the internet — making them untraceable.

Possessing a fully automatic gun is heavily regulated under federal law and only licensed firearms dealer can possess an auto-sear — and then only after paying a special tax, says Rob Doar, political director of the Minnesota Gun Owners Caucus. While he says that he's known of the devices being used recreationally, they more often are obtained illegally by those who lack training.

Shane Hallow, president of the Hennepin County Association of Paramedics and EMTs, the union that represents Hennepin EMS medics and dispatchers, says the presence of automatic weapons raises the likelihood that a victim is shot multiple times or that more than one person is struck. Either way, he said, this "further complicates treatment" and lowers a patient's chances of survival.

"If you're shot three to four times in rapid succession in your torso, that's more likely to hit major arteries or organs that would cause you to be critically ill or kill you almost immediately," he said.

The devices often are purchased online from companies in China and shipped under innocuous-sounding labels. This was the case in 2019 when customs officials in Chicago intercepted a suspicious package from a Beijing address that was bound for an apartment building in Woodbury, court records show. Authorities found two fully automatic trigger sear devices in the package, which was sent to federal agents in Minnesota. Agents arranged for a U.S. postal inspector to deliver the package to a man at the address. It wasn't immediately clear whether charges were filed.

In an unrelated federal case, a St. Cloud man who pledged loyalty to the anti-government group Boogaloo Bois pleaded guilty last June to illegally possessing two auto-sears.