AMNA NAWAZ: Fifty years ago, the Central Intelligence Agency unveiled a memorial to CIA members killed in service to the country.

It was first established with typical institutional quiet in the original headquarters' lobby.

Today, the Memorial Wall has become hallowed ground.

Nick Schifrin has this rare look from Langley, Virginia.

NICK SCHIFRIN: It is the intelligence community's most solemn site, 140 stars carved into Alabama marble, a permanent memorial, each star one life lost, but also a nameless, collective commemoration of sacrifice.

Killed CIA members get the same star, no matter seniority, and each star born from this Virginia studio.

Tim Johnston carves a replica destined for the fallen's family, using the same decades-old stencil, leading with perfect symmetry to a single, central point.

Johnston has been carving the Memorial Wall stars for 35 years.

TIM JOHNSTON, CIA Memorial Wall Carver: I don't get but one shot, and I can't mess up, you know, carved in stone, as the old saying goes.

NICK SCHIFRIN: Johnston took over from his mentor and the man who built the wall and its initial stars, Harold Vogel.

That was five decades ago, when the wall had 33 stars.

By 2003, there were 80.

Today, there are 140.

TIM JOHNSTON: The meaning behind the people and the work that they have done and the sacrifice they made, I mean, every star is a life.

NICK SCHIFRIN: When you walk into CIA and you see that Memorial Wall and the stars, what do you think?

CALISTA ANDERSON, Daughter of Jennifer Matthews: Each one of those stars represents a familial sacrifice that I understand way too well.

NICK SCHIFRIN: Calista Anderson and her father have tried to visit the Memorial Wall every year since her mother, his wife, Jennifer Matthews, was killed in 2009 in Afghanistan by a suicide bomber whom Matthews, CIA's counterterrorism personnel, and CIA leadership thought was an al-Qaida mole.

What do you see in her face when you look at that photo?

CALISTA ANDERSON: I almost see my own face, to be honest with you.

I just remember her as such a great mom.

She was just such a, I mean, effervescent person and really bubbly, just really caring and made a lot of effort to know us as kids and, like, know our personalities and talk with us.

NICK SCHIFRIN: Matthews worked for CIA's Alec Station, responsible for tracking al-Qaida and hunting Osama bin Laden.

At CIA, she knew al-Qaida as well as anyone.

CALISTA ANDERSON: One of her co-workers even told me one time: "I think she forgot more about al-Qaida than I ever knew about it."

So it's sometimes really nice to hear.

And then sometimes I'm almost in awe of my own mom.

NICK SCHIFRIN: That knowledge came later.

Anderson and her younger brothers didn't even know where their mom worked.

When Matthews died, her daughter was 12.

CALISTA ANDERSON: I never got to pick out a prom dress with her.

I'll never pick out a wedding dress with her.

So, things like that can be really difficult.

But I'm extremely grateful for the grief, because, as people say, it's an echo of lost love.

So, for me, I will have the grief for the rest of my life.

I don't think it'll ever go away.

But I'm really grateful that I'm able to feel that because I felt so much love.

NICK SCHIFRIN: Anderson has avoided dramatic depictions of her mother, including the film "Zero Dark Thirty," as well as a CIA after-action report acknowledging lapses across the agency that contributed to the death of Matthews and six other CIA officers.

CALISTA ANDERSON: I understand from an institutional point of view that that question is very important, but, from the point of view of myself, my mom was already gone.

I miss my mom.

Like, that's -- that's not a organizational figure to me.

That's not a worker or a job position.

She's a real person and a real family member who I no longer have in my life.

WILLIAM BURNS, CIA Director: For my colleagues here at the agency, for me personally, the wall is not an abstraction.

You know, each of those stars as a profound human story behind them.

NICK SCHIFRIN: Bill Burns is the director of the Central Intelligence Agency.

He looks at these stars and feels collective and personal loss.

WILLIAM BURNS: One of them is a very good friend of mine, Matthew Gannon, with whom I served four decades ago, my first post as a young career diplomat.

He was killed in the terrorist bombing of Pan Am 103 over Lockerbie, Scotland, on his way home from a temporary assignment in Beirut to his wife and two young daughters for Christmas.

It reminds me that this is an intensely human profession.

We are a human intelligence service.

NICK SCHIFRIN: When CIA created the wall 50 years ago, the agency was under siege, accused of co-opting student groups and NGOs, training domestic police forces, and abuses in Vietnam.

And in 1973, President Nixon fired director Richard Helms for refusing to assist in the Watergate cover-up.

His replacement, James Schlesinger, forced 7 percent of the agency to retire and was described as Nixon's revenge.

Was the wall in some ways a rehabilitation?

WILLIAM BURNS: For all of those problems and mistakes and flaws that you just described, which were very real, there was also a legacy of courage and dedication and patriotism too.

And so I think, in that sense, it was a part of that renewal, I think, at the agency, but also to remember the sacrifice that marks this agency and does to this day.

NICK SCHIFRIN: What do you see in your father when you look at these photos?

TIM WELCH, Son of Richard Welch: Well, this first one is dad, really, when he still had some hair.

NICK SCHIFRIN: Tim Welch lost his father 49 years ago, Richard Welch, assassinated at 46 years old, when he was the CIA's chief of station in Athens.

TIM WELCH: This is may of 1975.

He's pinning my second lieutenant Marine Corps bars on me.

This is for merit.

This is the Intelligence Medal of Merit.

Extremely proud of my father, smartest guy in the room, great sense of humor, great empathy.

Hero worship in the sense that, yes I saw this guy sort of going -- getting on planes and going all over the world and being promoted, got to a very high -- very high rank.

NICK SCHIFRIN: At the time, Dick Welch was the CIA's highest ranking officer killed while on duty.

He received full military honors and was buried in Arlington National Cemetery, normally reserved for military.

His funeral was attended by President Ford, National Security Adviser Brent Scowcroft, and Secretary of State Henry Kissinger.

Welch admits his father prioritized his career over his family.

But even decades later, grief is like a permanent hole that sometimes opens up.

TIM WELCH: The last time I saw him, I drove him to JFK, to the TWA terminal.

And we had a goodbye beer at the TWA terminal.

And, uh, that was -- that was -- I can still remember seeing him go down, you know, the Eero Saarinen TWA with those bright red carpets they had.

And so I can still remember him going down to the plane there.

NICK SCHIFRIN: Is it hard still to talk about this sometimes?

TIM WELCH: Of course.

It comes and goes.

NICK SCHIFRIN: Welch's killer wasn't caught for a quarter-century, past the statute of limitations, so no one was ever charged with the murder.

TIM WELCH: In our family, we have a very clear idea.

We do not consider ourselves victims.

We do not consider him a victim.

And we don't talk about closure.

He was doing a tough job.

He knew what he was doing.

And, as far as we're concerned, he died in the line of duty doing what he wanted to do in the service of the United States.

NICK SCHIFRIN: At the time, CIA kept a book of the fallen, some names still secret.

This photo of the original book has never before been public, its final name, Richard Welch.

Today, that book lives inside the case that holds a new book, which is double in size.

And every year, CIA holds an annual memorial ceremony for the families.

TIM WELCH: We all attended the ceremony in May.

being there with the family, with the agency family.

And, you know, now we're -- older guy.

And we go there and we see young kids who are bereaved.

CALISTA ANDERSON: Allowing us to be there and almost have a sort of catharsis grief moment among sort of your family and the people who best understand and best share it with you.

NICK SCHIFRIN: A family whose sacrifice is forever carved in stone.

For the "PBS News Hour," I'm Nick Schifrin in Langley, Virginia.