Keri Mungo is co-founder and CEO of SABG--the Strategic Alliance Business Group--which provides technical services for the federal government, including the Missile Defense Agency and the Department of Defense. Prior to starting her company, she spent four years in the Army and worked at the Pentagon--a job she left several months before September 11, a decision that will stay with her the rest of her life. --As told to Kevin J. Ryan

I joined the Army in April 1997. After boot camp and school, I was sent to South Korea. My company met people when they got off the plane and determined where within the country they were needed. It was an interesting job. 

My first sergeant had just come from the Pentagon. I was on orders to go to Fort Worth when I finished in Korea, but she convinced me I should take a role at the Pentagon. I reported to Lieutenant General Timothy Maude, the Army's deputy chief of staff for personnel.

I started at the Pentagon in January 1999. I was working in the management support office. That's where I met Sunny Pak Wells. She and I were both lower Army ranks, and there weren't a whole lot of us in the Pentagon, so we were propelled together immediately. Every morning, we would get coffee and chitchat before work.

We spent a lot of time together outside of work. On weekends, she and her fiancé, Chris, would come over and play gin rummy with me and my husband at the time. She and I usually were partners and would try to beat our significant others. She was my best friend. 

One day, General Maude's secretary got a new job and left. He needed a new secretary quickly. They pulled me in and I started working for him while they looked for a permanent replacement.

At the time, I was getting ready to transition out of the military. I decided I'd ask General Maude if I could keep working for him as his secretary, since it was a civilian job. I was so nervous to ask. 

He said no. I was kind of caught off guard. He told me, "What you're doing now is going to help you in the future, but you're going to do bigger and better things." He wrote me a letter of recommendation and got me my first job interview. The interviewer's wife had worked for General Maude, and he said, "If you can work for General Maude, you can work for anyone, so you've got the job." 

I left the Pentagon in March 2001. Sunny ended up taking my old position. To replace our coffee meetings, we started a ritual of calling each other and talking a little bit before we started working. 

This kind of tells you that God has a hand in everything, but Sunny's birthday was September 13 and her fiancé's was September 10, so she was going to be in the office only a couple of days that week. 

That particular morning, we were just kind of gossiping. Sunny had TVs in her office. She was like, "Did you see what happened in New York?" At that point, we didn't know that both towers had been hit. We didn't know how serious it was. We thought it was an accident. 

Suddenly, she screamed and the phone went dead. I tried calling her back and got a busy signal. I still knew the extensions in that office. I would call a number, get a busy signal. Call another number, get a busy signal. All of a sudden, it hit me: Something had happened.

Someone came running into the room and said, "There's been an explosion at the Pentagon." And immediately I was like, oh, my gosh. I called Chris and told him what had happened. He got in his car and drove to the Pentagon.

There was a lot of hope that she was unconscious in some hospital somewhere and we just needed to find her, so we started making calls. That went on for a couple of days. Then there was hope that they might find her stuck somewhere in the building. After a week or so, we finally had to give up hope on that. 

A few weeks later, Sunny's family got the call that they had found her. Her desk had been right near the area that got hit. Around that time, we found out that General Maude had died too. They were renovating the Pentagon when the attacks happened, and their team had been moved there just a few weeks prior.

There was a lot of guilt. Had General Maude let me take the secretary job, it would have been me. And great sadness. It was really difficult to lose her and to lose such a good mentor to me as well.

Sorry. I just don't talk about it very often. 

We ask employees for stories about a hero they know, and then try to honor that person.

I worked a few different jobs over the next few years. I met my husband, Adam, when we were both working for the Defense Information Systems Agency in 2003. That job let me see how the contracting world worked. A lot of it is networking and knowing people. I realized all those years I had spent in the military and the people I'd worked with were going to help me get to the next step.

We officially founded SABG in 2013. We provide programmatic and technical support for the most advanced military systems in the world. Our biggest client is the Missile Defense Agency, where Adam and I both worked for several years before we broke away and started SABG. We've grown to 150 employees. 

I remember when I worked for General Maude, my son was 6 months old and had to have ear tube surgery. General Maude called me after the surgery. He took time out of his day to ask how my son was, how I was, whether I needed anything. I just remember thinking he cared. I want those types of things to transcend what our employees do for our company. I want them to know: You're not just a number, you're not just somebody I'm selling off to the government. I want you to feel like you're a part of this. You're a part of making us all successful. 

We've started something that we call Honoring a Hero. We ask employees for stories about a hero they know, and then we try to honor that person on social media and in the company newsletter.

I don't think I'll ever be the same person I was before. That day really changed everything, even my relationships at the time, and kind of pushed me in a whole other direction. 

Something like that makes you recognize the opportunities you've been given and be more grateful for them. Sunny and General Maude didn't get those opportunities. They didn't get to go on and live the life that I've been able to live. In my work and in my life, I try to make sure I'm honoring them.

From the September 2019 issue of Inc. Magazine