There was a moment, Mayor Cory A. Booker of Newark said Friday, when he “thought we were not going to make it.”

“No air,” he said. “I just could not breathe. That’s when I thought, if I don’t find this woman in a few minutes, we’re both going to die.”

Less than 12 hours earlier, Mr. Booker had run into a burning house on his street and carried a woman to safety, but only after arguing with a police detective assigned to protect him who tried to restrain him and even reached out and grabbed his belt. “It was just one of these moments in life when you just decide to jump in,” the mayor said.

Mr. Booker has had other moments in life when he had jumped in, and he has not hesitated to talk about them — or, late Thursday night, to send out a message alerting his Twitter followers. There was the time when a teenager was hit by gunfire and died in his arms. There was the time when a drug dealer named T-Bone threatened to kill him. Later on, T-Bone broke into tears as he asked Mr. Booker for help in getting his life on track. And, as mayor, he is known, according to several people who have worked with him, for keeping an ear tuned to the police scanner in his security detail.