The dashboard shook. Hot coffee slopped over my hand. I shouted, “What the hell?” A few moments later the radio sputtered, the dispatcher calling out, “Reports of an explosion at Market and Fourth. Nearby units identify and respond.”

I dumped my coffee out the window, grabbed the mic, and told Dispatch we were two blocks away as Conklin accelerated up the hill, then braked so that our car slewed across Fourth Street, blocking traffic.

We bolted from the car, Conklin yelling, “Lindsay, watch out. There could be secondary explosions!”

The air was opaque with roiling smoke, rank with burning rubber, plastic, and human flesh. I stopped running, wiped my sleeve across my stinging eyes, and fought against my gag reflex. I took in the hellish scene — and my hair literally lifted away from the back of my neck.

Market Street is a major artery. It should have been pulsing with commuter traffic, but instead it looked like Baghdad after a suicide bomb. People were screaming, running in circles, blinded by panic and a screen of smoky haze.

I called Chief Tracchio, reported that I was the first officer on the scene.

“What’s happening, Sergeant?”

I told him what I saw: five dead on the street, two more at the bus stop. “Unknown number of victims alive or dead, still in their cars,” I coughed into the phone.

“You okay, Boxer?”

“Yes, sir.”

I signed off as cruisers, fire rigs, and EMS units, their sirens whooping, streamed onto Market and formed a perimeter at Third and at Fifth, blocking off oncoming traffic. Moments later, the command vehicle rolled up, and the bomb squad, covered top to toe in gray protective suits, poured onto the debris field.

A bloodied woman of indeterminate age and race staggered toward me. I caught her as her knees buckled, and Conklin and I helped her to a gurney.

“I saw it,” the victim whispered. She pointed to a blackened hulk at the intersection. “That school bus was a bomb.”

“A school bus? Please, God, not kids!”

I looked everywhere but saw no children.

Had they all been burned alive?

Three

WATER STREAMED from fire hoses, dousing flame. Metal sizzled and the air turned rancid.

I found Chuck Hanni, arson investigator and explosion expert, stooping outside the school bus’s side door. He had his hair slicked back, and he wore khakis and a denim shirt, sleeves rolled up, showing the old burn scar that ran from the base of his right thumb to his elbow.

Hanni looked up, said, “God-awful disaster, Lindsay.”

He walked me through what he called a “catastrophic explosion,” showed me the two adult-size “crispy critters” curled between the double row of seats near the driver’s side. Pointed out that the bus’s front tires were full of air, the back tires, flat.

“The explosion started in the rear, not the engine compartment. And I found this.”

Hanni indicated rounded pieces of glass, conduction tubes, and blue plastic shards melted into a mass behind the bus door.

“Imagine the explosive force,” he said, pointing to a metal projectile embedded in the wall. “That’s a triple beam balance,” he said, “and I’m guessing the blue plastic is from a cooler. Only took a few gallons of ether and a spark to do all this…”

A wave of his hand to indicate the three blocks of utter destruction.

I heard hacking coughs and boots crunching on glass. Conklin, his six-foot-two frame materializing out of the haze. “There’s something you guys should see before the bomb squad throws us outta here.”

Hanni and I followed Conklin across the intersection to where a man’s body lay folded up against a lamppost.

Conklin said, “A witness saw this guy fly out of the bus’s windshield when it blew.”

The dead man was Hispanic, his face sliced up, his hair in dyed-red twists matted with blood, his body barely covered in the remnants of an electric-blue sweatshirt and jeans, his skull bashed in from his collision with the lamppost. From the age lines in his face, I guessed this man had lived a hard forty years. I dug his wallet out of his hip pocket, opened it to his driver’s license.

“His name is Juan Gomez. According to this, he’s only twenty-three.”