The last arrest on Labor Day in the Gresham District stemmed from a call just before 10 p.m. There was someone with a gun near 78th and Loomis — just blocks from where two people had been wounded in separate shootings that weekend.

The first two Chicago cops to arrive spoke with a man who said he’d been threatened when he tried to drive around a stalled car in the alley. He told them a guy jumped out of the car and informed him, “I’ll blow your m—–f—— a– up,” gesturing toward his waistband as if he had a gun, according to the police report.

The officers soon found the 39-year-old man who’d allegedly made the threats. Charging him with assault, they hauled him in.

The station had been relatively quiet that day. Gresham is usually one of the city’s busiest districts and Labor Day among the busiest times of the year. But this was just the sixth arrest in the South Side district that day — not even half the number arrested on Labor Day a year earlier and less than a third compared with 2014, reflecting a citywide drop this year in arrests.

As Chicago grapples with a surge in killings and a mistrust of law enforcement stemming from police shootings, the number of arrests in the city has fallen by 28 percent versus last year, a Chicago Sun-Times analysis finds.

The number of arrests in Chicago this year is on target to be the city’s lowest since at least 2001, according to the Sun-Times analysis of city crime data, which also found:

• Through mid-December, police were on pace to make about 50,000 arrests citywide in 2016 — down from over 69,000 a year ago. The year’s current arrest total is less than half what it was in 2010, the year before Mayor Rahm Emanuel took office.

• The drop is steepest in areas such as Englewood and Austin where violence is common and police have long flooded “hot spots” and drug markets. But the decline isn’t limited to high-crime areas: Arrests are down by double digits in every district in the city.

• Arrests have fallen in every major crime category included in the city’s online database, from theft to aggravated battery with a handgun — the most common charge for a nonfatal shooting.

• Narcotics arrests plummeted by half — the most dramatic decrease for any type of crime. That’s partly because of a state law that took effect this summer decriminalizing possession of less than 10 grams of marijuana. Chicago cops this year will make about 4,200 arrests for misdemeanor pot possession — down from 20,000 five years ago.

Police Supt. Eddie Johnson says the figures reflect the department’s focus on addressing gun violence and improving community relations.

“We want to arrest the right people at the right times for the right reasons,” Johnson says. “But just indiscriminately stopping people? No. We cannot arrest our way out of this.”

The superintendent says the department is moving away from decades of “broken windows” policing — a strategy that emphasizes heavy enforcement of even low-level offenses to send a message that crime won’t be tolerated. While that led to lower crime rates, it also worsened tensions in some neighborhoods where people felt the police were heavy-handed.

“The time when broken windows theories came in — I think it was effective,” Johnson says. “But we have to focus on what’s really hurting Chicago right now, and that is the gun violence.

“Don’t get me wrong — we have not abandoned locking people up for quality-of-life issues. But low-level narcotics offenses — we can continue to do that, but would it affect the gun violence we’re seeing? I doubt that.”

He adds: “I’m not a fan of mass incarceration. But if you decide to pick up a gun, pull the trigger and shoot somebody, I don’t care what your rap is, you should go to jail for it.”

Even amid the overall drop in arrests, the police are busting more people for gun crimes, Johnson says. So far this year, Chicago cops have made nearly 3,900 seizures for illegal guns accompanied by arrests — the highest total since 2012, according to police officials.

Still, the number of arrests for all weapons offenses — including the most common, the illegal possession of a handgun — has dipped slightly, the Sun-Times analysis shows.

Johnson rejects the idea of the “Ferguson effect” — the theory that violence has risen because cops have been holding back amid protests over police shootings in Ferguson, Mo., and other cities. Yet he acknowledges that many police officers feel “vilified,” and others have been slowed down as they learn new legal requirements for documenting street stops.

“But I think the police officers in Chicago are working just as hard,” he says.

The decline in arrests is welcomed by civil rights groups.

“Our perspective is: The fewer people in jail, the better it is for our communities,” says Deangelo Bester, executive director of the Workers Center for Racial Justice, which focuses on access to jobs.

Instead of responding to violence by locking up nonviolent offenders, city officials could divert funds from the police department and into neighborhood development, Bester says.

“Chicago is the most-policed city in the country,” he says. “Maybe it’s time to do something different.”

Natalie Howse, president of the Cook County Bar Association, says the African-American lawyers group supports “policing that is more concerned with respect for the rule of law and individual rights, rather than the number of arrests.

“If the Chicago Police Department has placed greater focus on reducing the violent crime that plagues our city, and that new emphasis has temporarily resulted in fewer arrests of non-violent offenders, the CCBA welcomes that strategy so long as the cost is not allowing black communities to descend into lawlessness.”

Bester says it’s not yet clear whether the police department is changing its long-term strategy or whether officers are responding to criticism by slowing down. “It could be they’re throwing a little temper tantrum the only way they know how,” he says.

Some rank-and-file officers say cops aren’t being less aggressive as an act of protest but because they’re worried they’ll be caught on video making an honest mistake, then blasted for it.

“You’re being Monday-morning-quarterbacked for everything,” says one officer, speaking only on the condition of not being named.

Others say that’s not acceptable, arguing that body cameras and increased documentation will help police do their jobs.

“Those people are looking for an excuse,” says a veteran North Side supervisor, also speaking only on the condition of anonymity. “What they’re saying is that I liked it better when no one was recording when I trounced on someone’s head.”