"I just looked up and seen a baby stroller getting pushed by the wind and I just took off after it," he told Eyewitness News.
Video of that horrifying moment - which has gone viral and has garnered millions of views - shows the baby's great aunt launching herself toward the stroller to stop it but missing it.
Nessman was at a nearby carwash at that moment with his sister.
"So I take off running and by the time I caught it, it was at the top of the driveway," he said.
Nessman grabbed the stroller right on time then reunited the baby boy with his great aunt, giving her a reassuring hug.
READ MORE | Video shows man rush to stop runaway stroller with baby right before it rolls into busy street
Video shows man rush to stop runaway stroller with baby right before it rolls into busy street
It just so happened that Nessman had been at the location following a job interview for a dishwashing position at Applebee's.
"Anybody would have did it, just right place at the right time," he said.
Fortunately, things are looking up for Nessman after years of consuming grief in the wake of his girlfriend's death, which led to homelessness, addiction and time as an inmate.
He said he's currently healing and putting his life back together and his heroics are providing him with a renewed sense of purpose.
"I got a job and people wave to me on the street," he said. "I guess I was here for a reason."
Nessman completed his orientation with Applebee's and his first day on the job will be Saturday night.
He said he's hopeful his story will encourage someone else to react when they see someone in need.
Nessman said a GoFundMe page has been created asking for donations on his behalf but said he's not asking for money or anyone to contribute to the page.
Instead, he's just happy the outcome was a positive one.