It was 40 years ago today that serial killer David Berkowitz murdered his first victim in the Bronx, the start of a yearlong reign of terror that left New Yorkers both on edge and fixated with what became known as the Son of Sam murders.

At the time I was 12 years old. A few months later I started to deliver The Daily News to apartment buildings in the Bronx.

The killings, which also came to be known as the work of the .44-Caliber Killer, because of the weapon he used, were ready-made fodder for the city tabloids and TV stations.

The serial murders came at a time that I was coming of age. I was asserting my independence – I was working and starting to ride the subways by myself.

So for me, the city was both exciting and dangerous. (Remember, New York was just coming out of its dismal fiscal crisis and crime, poverty and drugs were tearing at the fabric of its communities.)

It was against this backdrop that the Son of Sam killings gripped the city’s attention. Over the course of more than a year, he shot 13 people in cold blood, killing six.

Berkowitz, who later claimed he was acting on instructions given to him by a neighbor’s dog, played cat and mouse with the cops, taunting them with handwritten letters to Daily News columnist Jimmy Breslin.

The murders were intermittent. This was not a one-time spree killer like the mass shootings now all too familiar to us today.

Instead, Berkowitz targeted young couples, often in parked cars, and frequently young attractive women with long brown hair. (This reportedly prompted many young women in the city to run to salons to get their hair dyed a different color.)

As a newspaper delivery boy, I would get stacks of The Daily News delivered outside our apartment door for me to then distribute to my customers.

That, in turn, meant I got a jump on all the latest developments in the case.

I would voraciously read the stories before I headed out on my route.

Among the headlines: “Breslin to .44 Killer: Give Up! It’s the Only Way Out!’ “Cops: .44-Caliber Killer ‘Is Taunting Us.’” “New Note: Can’t Stop Killing.” “Killer to Cops: I’ll Do It Again.”

The day after cops arrested Berkowitz – Aug. 11, 1977 – The Daily News featured this headline: “Nab Mailman as .44 Killer.”

I rushed into my parents’ bedroom and breathlessly woke my mother.

“They got him! They got the .44-Caliber Killer!” I told her.

Indeed they had.

And a 13-month reign of terror had finally come to an end.