Esau Marquez, a bicycle food deliveryman for a new app called Uber Eats, was wheeling down Market Street in San Francisco last Monday when he came upon a chaotic scene.

People were yelling and screaming around a pool of blood at the 5 and 21 Muni stop. One woman stood frozen in a terrified daze.

Marquez, who had recently been threatened by a man with a knife in the Mission District, assumed someone had been stabbed. He jumped off his bike to offer assistance.

"I saw this woman standing in a state of shock," Marquez said. "Blood was everywhere. There were two people right next to her and one was screaming. I thought one of them had stabbed her and I'm going to have to take her (down)."

But then Marquez looked down. A baby boy was lying on the pavement next to a bloodied placenta.

A 47-year-old father of two, Marquez knew exactly what to do.

"I took my jacket off and wrapped it around the baby," Marquez said. "My wife delivered two children. I saw doctors deliver them. My instincts kicked in."

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A witness, Ayrron Comini, said the mother, whose name is unknown, never made a sound during the birth and that Marquez was one of the few people to help.

"I watched the guy jump off his bike, take off his shirt and wrap it around the kid and cradle the baby," said Comini, who deejays at the Crazy Horse, a strip club adjacent to the Muni stop.

"The mother was just in shock. She didn't move.

"Everyone was standoffish. But he jumped in and probably saved that baby's life."

Marquez says the baby wasn't moving as he held him, but a woman shouted out to slap the infant on the back.

"It's a good thing that woman said that because I was like on Cloud 9 with this baby and thinking about my own kids.

"I was looking into its little face and reminiscing about looking into my own children's faces.

"When I slapped the baby on the back, it started crying and breathing."

The fire department arrives

San Francisco Fire Department responders and police arrived at the scene shortly after the birth. SFFD public information officer Mindy Talmadge could provide few details about the incident, but she said the woman wasn't aware she was pregnant and "she had an altered mental status."

Talmadge added that the baby was born premature at 32 weeks and the mother and child were in good condition at the time of transport to San Francisco General Hospital.

Hospital information officer Brent Andrew could only confirm that the woman checked out of the hospital.

Comini said Marquez is a hero. "Nobody else stepped up, but he did," he said. "He literally took the shirt off his back and took care of that baby."

Marquez dismisses the hero talk.

"This guy is like 'Dude, you're a hero!' I said, 'No, I'm not a hero.' I just did what needed to get done," he said.

"It was so cold, and no one else was willing to sacrifice to pick up this child."

When the Fire Department arrived, Comini invited Marquez inside the Crazy Horse to wash his hands. Comini gave him a clean T-shirt.

"When I walked into the Crazy Horse, I thought, if my wife sees me walking into here she'll kill me," Marquez said. "He (Comini) also gave me a pen and said, 'Dude, you can come and see my girls any time."

When Marquez returned home and shared the story with his wife, she was anything but mad.

"She was just like, 'Wow,'" Marquez said. "Very proud."

The birth was captured on video (above) at the scene by an unidentified witness. KRON ran an edited version of the footage in a news segment.