The sudden, mid-day blast roared through the Loop.

Its force blew the windows out of the Marquette Building. Four people died. Dozens were wounded. And a substitute mail carrier whose name would become a cultural icon nearly lost his life.

One hundred years ago Tuesday, someone tossed a bomb into the Adams Street entrance of Chicago’s old federal building. The blast, around 3 p.m. on a Wednesday, shook the massive edifice at Adams and Dearborn, which filled with flames and dust.

Touched off by an act of early 20th Century terrorism near the end of World War I, the pandemonium that ensued was described in detail by the Chicago Daily News, which called it a “death bomb.” Authorities vowed to bring the bomber to justice.

“Every known opponent of the prosecution of the war, every moron, half wit and insane person hitherto considered ‘harmless’ not already in custody of federal, state or city authorities, was being herded into detention today in an effort to seize upon the guilty,” the Daily News reported.

Walt Disney was apparently among the many postal workers inside the building at the time. Disney once said in an interview that he barely missed the blast on Sept. 4, 1918 — a decade before the world met Mickey Mouse.

“They had a big bombing during the first World War,” Disney said in that 1956 interview. “I was right in the lobby when whoom! This thing went off, and here comes dust shooting out and everything, and that was the way I went out every night. I missed that, missed that darn thing by about three minutes.”

Disney also said the bomb killed “a mailman who worked just two desks from me. He was on his way out and got killed.” The two postal workers left dead by the explosion were Edwin Kolkow, a Civil War veteran, and William Wheeler.

Also killed were sailor Joseph Ladd and Ella Miehlke. Witnesses said Ladd was standing on the Adams Street steps and talking to Miehlke when they were thrown into the street by the force of the bomb. Wheeler had been in the doorway and was also reportedly thrown into the street.

Authorities compared it to the 1886 Haymarket bombing and promised that “everyone connected with this outrage will be summarily dealt with.” Among those rounded up in the investigation was Nina Van Zandt Spies, according to the Daily News. Her husband, August Spies, was hanged in 1887 after the Haymarket riot.

But true suspicion fell on the Industrial Workers of the World, a radical labor group. Judge Kenesaw Mountain Landis had days earlier sentenced about 90 I.W.W. members for obstructing the war effort, giving 20 years to leader William “Big Bill” Haywood and others. The day of the bombing, Landis was on the sixth floor of the federal building. He would later become commissioner of baseball.

Meanwhile, the lone official found at the I.W.W.’s Madison Street headquarters after the bombing denied the group had any role in it, telling reporters, “the I.W.W. is the national scapegoat.”

Though the explosion ripped a hole in its side, the federal building’s foundation apparently escaped damage. It wouldn’t be demolished until 1965 — following the trials of Al Capone and James Hoffa — to make way for today’s federal plaza.

Despite the intense investigation and promises of justice in the 1918 bombing, no one would ever be convicted for the deadly explosion.