On the morning of March 1, Lebrón traveled to Grand Central Terminal in Manhattan, where she rendezvoused with the rest of the group. They took the train to the Capitol. Rafael Cancel Miranda suggested they postpone the attack, as it was late and the weather was rainy.

Lebrón refused. She continued towards the Capitol building's interior. The group looked at each other, and decided to continue with their mission.

When the group reached the visitor's gallery above the House chamber, they sat while the representatives discussed the Mexican economy and immigration. After Lebrón gave the order, the group recited the Lord's Prayer. She then stood up and shouted, "¡Viva Puerto Rico libre!" and unfurled the flag of Puerto Rico. The group opened fire with semi-automatic pistols toward the Representatives below.

Some 30 shots were fired (mostly by Cancel, according to his account), wounding five lawmakers. Wounded were Alvin Morell Bentley (R-Michigan), who took a bullet to the chest, Clifford Davis (D-Tennessee), hit in the leg, Ben F. Jensen (R-Iowa), shot in the back, as well as George Hyde Fallon (D-Maryland) and Kenneth A. Roberts (D-Alabama). All of them survived.

The group was immediately arrested. Upon her arrest, Lebrón yelled, "I did not come to kill anyone, I came to die for Puerto Rico!" Lebrón said she intentionally fired her shots at the ceiling. Figueroa's pistol had jammed.

The shooters were charged with multiple counts of assault with intent to kill. During her trial, Lebrón said she came not to kill, but "to die for the liberty of her homeland." The accused were the only ones to testify in their defense.

In June 1950, all four shooters were found guilty. The jury, apparently believing Lebrón's testimony, found her guilty of lesser charges of assault with a deadly weapon. The judge sentenced Lebrón to 16 to 50 years in prison, and each of the three men to 25 to 75 years in prison.

The group was then charged with "seditious conspiracy to overthrow the United States government by force." So were more than two dozen others. The indictment alleged that the defendants were "active members, leaders, officers or persons in control of the Nationalist Party of Puerto Rico, which is charged to be an organization dedicated to bringing about the political independence of Puerto Rico from the United States by force of violence or armed revolution."

This time, the group vigorously contested the charges. The defense called five witnesses to testify that the Nationalist Party did not advocate for the overthrow of the U.S. government and only sought total independence for Puerto Rico.

Julio Pinto Gandia, the alleged leader of the group in the U.S., told the court that the Party, founded in 1922, was not "a band of terrorists" and that any violent actions arose out of individual "despair."

When Rafael Miranda, the shooter who directly fired at Congressmen, was 7 years old, his mother and father traveled to participate in a nationalist march. He and his sisters couldn't attend since they were all sick with measles.

As it turns out, they had incredibly lucky timing.

That march was where the Ponce massacre happened. Protesters were chased by the police and shot or clubbed at the entrance of their houses as they tried to escape. Others were taken from their hiding places and killed. Leopold Tormes, a member of the Puerto Rico legislature, told reporters how a policeman murdered a nationalist with his bare hands.

Dr. José N. Gándara, one of the physicians who assisted the wounded, testified that wounded people running away were shot, and that many were again wounded by the clubs and bare fists of the police. No arms were found in the hands of the civilians wounded, nor on the dead ones.

The white nurse's uniform of Miranda's mother was soaked with blood as she crawled over bodies in search of her husband. Miraculously, the two both managed to return home unharmed.

Miranda never forgot this incident. Shortly after the march, he committed his first political act. During his first grade class, he refused to salute the American flag.

One lawyer for the group pointed out that the charge made it so that mere membership in the Nationalist Party was a crime, and that not all of those charged had committed individual crimes. He told the jury that the government was trying "proscription of a dissenting political group because of its ideas."

There were three sedition trials held against the Puerto Rican nationalists between 1954 and 1955. Four testified for the prosecution and received suspended sentences. Of the rest, all but one of them were found guilty.

The Congress shooters each had six years added to their sentences. The others received prison terms ranging from 18 months to six years.

The four were sent to different prisons: Cordero to the federal penitentiary in Atlanta; Lebrón to the women's prison in Alderson, West Virginia; Miranda was to Alcatraz, and Flores to Fort Leavenworth.

Lebrón's son and mother died during her first two years in prison. She refused to accept letters from her sister because only letters written in English were permitted in the prison. A group of judges offered her parole in exchange for a public apology, which she rejected.

Lebrón became eligible for parole in 1979. However, she refused to apply, citing her political beliefs.

In 1977, President Jimmy Carter ordered the release of Cordero, who was dying of cancer, on medical grounds. In 1979, he granted clemency to the other three shooters. They were were welcomed back as heroes by thousands of nationalists in Puerto Rico.

It is generally agreed that Carter's commutations were politically motivated. Carter said he thought they'd served enough time. However, one of his aides said "they are less a cause célèbre outside of jail than inside."

A week after their release, at receptions in Chicago and New York City, the four demanded Puerto Rican independence and refused to rule out violence. During a press conference at the United Nations, Lebrón said, "I am a revolutionary and a member of the atomic age. I hate bombs but we might have to use them."

However, Lebrón's days of violence were over. She continued to write books and speak out in favor of the movement, but the violence of the Puerto Rican independence movement lost traction in the late 1970s, and virtually ended in the late 1980s.

Cordero died of cancer on March 7, 1979. He was 54.

Flores died on March 20, 1994. He was 69.

Lebrón died on August 1, 2010. She was 90.

Miranda died on March 2, 2020. He was 89.

Puerto Rico remains a territory to this day. The independence movement is a shadow of its former self.