Los Angeles ? He thought he was going to die.

He was having trouble breathing. As he lay wedged under a train seat and metal debris, he scrawled with whatever energy he could summon and a heartbreaking economy of words a farewell in blood on the seat. “I (heart) my kids. I (heart) Leslie,” he printed. The blood ink seemed to be running out as he got to the second sentence.

Capt. Robert Rosario, the firefighter who discovered that message, later choked up as he related the story for TV cameras. Of all the images, sad or brave, pulled from the mangled wreckage of Wednesday’s Metrolink train disaster, few captivated people more than this finger-painted testament of love. And none was more mysterious.

Who was the message writer? What happened to him? Who is Leslie?

Everyone wants to know. Los Angeles Fire Department spokesman Brian Humphrey said the department had been inundated with inquiries — “about 700 calls,” he said — from people who simply wanted to know who he was and how he was doing.

The mystery messenger was admitted to County USC Hospital, which received more than 100 phone calls from the public asking about him.

This much is known: Leslie is his wife. And his name is John. And he may not want the rest of the world to know even that much about him — no matter how much they crave that and more.

“I’m a private person,” he said in a statement the hospital released for him, “and the message that I wrote was a private message to my wife and my kids because I didn’t think I was going to make it.”

Los Angeles Fire Department spokesman Capt. Carlos Calvillo said he understood why even strangers were moved.

A man injured in Wednesday's train derailment near Los Angeles wrote a message to his wife and children, fearing that his injuries would be fatal. The man -- known publicly only as John -- was hospitalized after being pulled from the wreckage.

“The fact that this guy in this situation had the amount of love he had for his family, and for him to realize ‘I’m possibly going to die here’ — how could any words explain it?” said Calvillo, who watched as one of the rescuers speaking before the cameras choked on his account of John’s rescue.

“That moved firefighters as big and tough as we are,” Calvillo said. “We’re big teddy bears. It tremendously affected the guys in the 27th.”

The firefighters from a search and rescue unit at Los Angeles Fire Station 27 crawled through a rip in the wall of the second passenger car of the northbound train, which was tilted at an angle.

They pulled two bodies out. But someone had told them there was a survivor who needed help. They found John trapped in the rubble of metal debris and seat material.

“I can see why he thought he wasn’t going to make it,” Rosario said. “He said his ribs were hurting and he was bleeding from below the waist.”

Using the “jaws of life” extraction tool, the firefighters removed the debris that pinned John. Rosario whipped off the seat that had been pressing against his body. That’s when he saw the sad and bloody message on the seat.

The firefighter held the object that bore what John feared would be his last words. “If I could give you this seat,” Rosario told him, “I would.”

The rescuers quickly placed John on a back board and carried him out of the train.