Two passers-by rescued a 3-year-old boy who fell four stories, scrambling to catch him as he tumbled from a fire escape, police said.

Julio Gonzalez, 43, and Pedro Nevarez, 40, saw 3-year-old Timothy Addo dangling from a Bronx building on Thursday, police said. The boy had crawled out of a window when his baby sitter briefly took her eyes off of him, police said.

"He was hanging on for dear life," Gonzalez said.

Hearing people in the building scream for help as the boy's grip weakened, the men rushed over to position themselves under the fire escape to catch him.

"No one came," Nevarez said. "We knew it was up to us."

The boy tumbled and hit Nevarez in the chest so hard he knocked him off balance, but he bounced into Gonzalez' arms.

Timothy was treated at the hospital for a cut on his forehead.

"He's fine. He's happy. He's smiling," said his mother, 26-year-old Katrina Cosme, who was working at the time of the accident.

Police talked to the baby sitter, and an investigation was continuing Friday, Detective John Sweeney said.

The crucial catch came two days after a bystander threw himself onto a Manhattan subway track to save a man who had fallen, and a day after three police officers delivered a baby on a Brooklyn subway platform.

"This is the week of heroes in New York," Police Commissioner Raymond Kelly said.