Let’s say you’re at work and your phone buzzes. You pick it up expecting your 100th email or text notification of the day and instead read: “NEARBY! Burglary at [Your address].”

That’s the alert I got from Citizen, an app that notifies you about crimes in your area. In my experience, can be anything within a two-mile radius or so.

What do you do with this information? My building has about 50 apartments. Should I run home to defend my place? I decided not to.

I never got an answer about what actually happened in my building. Nothing of mine was missing, and my building manager’s theory was that someone may have been horsing around on the fire escape. Citizen’s only update came 18 minutes later: “Officers on scene are no longer requesting assistance.”

Still, it was the defining moment in my experiment with Citizen, which I had downloaded to write about.

One of the first things you see when you install and open the app for the first time is a breathless announcement that “this app could save your life.”

Soon after, you are warned: “Never approach a crime scene.”

If a witness is within a quarter mile of a recently active incident, a little “go live” button comes to life on their app.

Citizen is the born-again, hands-off version of an app that bit the dust because it seemed to suggest that witnesses to crimes step in — that one was named, appropriately, “Vigilante.”

This newer, cleaner, less morally questionable reincarnation recently reached a milestone: 150,000 notifications about incidents in the San Francisco area have gone out, so far.

In my experience, these came so frequently that I eventually barred my phone from playing the notification tone to keep my blood pressure down.

They ranged from alarming, to benign, to vague, to just bizarre.

“Person fatally shot.”

“Car break-in in progress.”

“Threats made.”

“Man pulled out sword on third floor.”

I started to ignore them.

Of course, not everyone shares my experience. Josephine, who lives on the border between Potrero Hill and the Mission and asked that her last name not be used, has come to rely on Citizen and feels much safer having it in her pocket.

She no longer has to rely on stale reports in the news or on Nextdoor to know what’s going on along her dog-walking route.

“That stuff is secondhand accounts from neighbors, or, with the news, it’s reported after the fact. The thing I really liked about Citizen is feeling like I’m dialed in real time,” she told me.

That feeling is, I predict, what will draw downloads from consumers of crime news — and, as we know from writing for Mission Local, people, despite themselves, love crime stories.

To some degree, everything is filtered, and everything is after the fact. The true extent of crime — and how to definitively avoid becoming a victim — is unknowable.

Citizen will not reveal how exactly it sources its reports. They are gathered from “Active crimes circulating in 911 and emergency broadcasts,” Citizen’s Lea Artz, a former television reporter and digital communications director for the NYPD, told me.

“We have people monitoring all emergency 911 broadcasts around the clock,” she said.

It’s unclear how this access happens. There is no official relationship between the SFPD and Citizen, or the Department of Emergency management and Citizen, just an “open dialogue.”

The monitors, comprised of “some people who are former law enforcement dispatchers, people with backgrounds in public safety, people who are interested in public interest journalism,” create headlines and updates that get pushed out to the users.

Whoever they are, there’s no denying that they are lighting fast.

If you are a Nixle subscriber — a text-message-based safety-alert service that includes things like power outages and gas leaks — you’ll love Citizen. When a deadly shooting broke out in the Fillmore in late October, Nixle alerted me of an event due to “police activity.” Great.

Citizen, by contrast, already had a report up more than 20 minutes earlier that three people had been shot, a brief suspect description and an alert that a bystander was livestreaming.

But if we’re honest, do we really want to know about all of the awful stuff that’s going on around us, especially when there is, by design, nothing we can do about it? Are we just swapping vigilantism for voyeurism?

Aren’t there cases in which the need for privacy outweighs the need to be informed?

“It’s something we think about a lot and keep an eye on,” Artz said. “There are cases where we don’t want something to be shown. … We had a woman commit suicide and someone was trying to livestream, and that video was blocked.”

And, as she pointed out, nobody is sharing video via the app that couldn’t be shared anywhere else — on a public street, anyone can and does film and post anything.

Still, some of what I was notified about made me uneasy. A fatal shooting at an address near my apartment turned out to be a man who had shot himself inside his home. One notification announced that there was a “domestic assault” ongoing at a specific address.

Or how about the “man standing in middle of traffic and flapping his arms” at 24th Street and South Van Ness? God help us if we reported on that last one as news with the premise of public interest — we’d be laughed out of town.

Perhaps the real game-changer of Citizen is contingent on critical mass.

“When everybody has the Citizen app, which is something we dream about a lot … the potential for tracking or capturing or following or all just doing our part to keep each other safe … that’s something that drives all of us,” Artz said.

Keep in mind, though, that users cannot generate a Citizen report. And, if you’ve watched the app’s promo video, which strongly suggests that in-app tools could help police catch a kidnapper, understand that there is no mechanism for relaying information from within the app’s chat function or live stream back to law enforcement.

I asked what people should do when they’re notified of something happening in a place where they have to go or that they care a lot about — their kid’s school, their home, their office.

“People should do the same thing they would normally do: use common sense to stay safe. Call 911,” Artz responded. “Citizen in no way advises people on what to do during ongoing incidents. We provide the relevant safety information to help the public make informed decisions about their personal safety.”