SAN FRANCISCO (KTVU) - A San Francisco dentist who chased down a would-be kidnapper says it just as easily could have been his own son snatched off the sidewalk.
"I think my fatherly instincts kicked in and I did what I thought was right," Adam Walker told KTVU, outside Orphan Andy's Restaurant at 17th Street and Castro Street.
The bold abduction attempt happened last Friday about noon in front of the restaurant.
Adam, with his wife Sabrina and 4-year-old son Leo, had walked past the woman victim moments before.
She was headed the same direction, with an infant in a front pack and a toddler by the hand.
When the Walkers heard a struggle, they looked back:
"She was screaming, 'Police Police help me', and we noticed there was a man walking past with a child in his arms, and she was not letting go." Everyone in the vicinity was startled, then alarmed.
"In the moment it was very scary, and you just can't imagine that happening to you," said Sabrina Walker.
Then, just as suddenly as he had grabbed the 2 year old boy, witnesses say 34-year-old Australian Roscoe Holyoake, turned him loose.
"He stopped and gave the boy back to the mom," described Walker, "and then he turned and smiled at us and took off running down the street."
Holyoake ran down the middle of 17th Street, with Walker and another witness chasing, and shouting for others to help.
Holyoake turned on Noe Street, but after racing half the block, and realizing several people were on his tail. he stopped.
"He put his hands up, and said 'all right, I'm done,'", recounted Walker, "and he didn't fight back, didn't struggle, just obeyed my commands, walked to the sidewalk and put his hands on the wall and got on his knees."
Nothing was said before police arrived.
"Honestly we were catching our breath, we were all out of breath, so there wasn't a lot of talking," said Walker.
In the meantime, Sabrina Walker stayed with the distraught mom and her children.
"Out in broad daylight when it's so crowded, this was a very, very scary experience," Sabrina told KTVU.
Once Adam made his way back, he was able to talk to the 32-year-old mom as well and she thanked him, relieved that Holyoake was in custody.
"The fact that he chose that child over mine, it could have been my child," said Walker, and if no one got him, and he got away, it could have been anyone else's child the next time."
Police investigators are looking into Holyoake's background and his time in the U.S.
"I think it was great they decided to help, it's very dangerous, but it's great they were able to help apprehend the suspect," said SFPD Public Information Officer Joseph Tomlinson.
Holyoake's facebook page shows he works as a DJ who goes by the name "DJ Roski".
News outlets in Australia describe him as a prominent radio host, often featured at LGBTQ events.
Now he is jailed on $500,000 on suspicion of kidnapping.
"We don't know what started this, why he decided to grab the child, we're trying to figure out some of those details," said Officer Tomlinson.
Numerous surveillance cameras on businesses in the area captured both the kidnap attempt and Holyoake's surrender.
Adam Walker says investigators who viewed the video gave him and the other Good Samaritans kudos for how they handled it.
Walker has no law enforcement training, but says with paternal instincts, he didn't need it.
"When you have a child of your own and you see something like that happen, something else just kind of takes over," Walker explained.
"You act from your heart and not from your brain. So it's fortunate everything worked out and no one got hurt."