MEXICO CITY — Luis Donaldo Colosio finished the last speech of his life and descended from the makeshift podium of a pickup truck into the chaos of a campaign rally in a Tijuana shantytown. The crowd pressed around the presidential candidate, jostling his entourage in the sloping dirt plaza.
As the dance tune "The Snake" blared suddenly in the background, a young man in black emerged from the crush, grasped Colosio's arm, placed a .38-caliber revolver against his head and fired.
Panicked aides carried away the mortally wounded Colosio. Bodyguards hustled the captured gunman to another vehicle, but its path was blocked by journalists, city police and citizens. They shouted that the assassin would be killed or disappear--and Mexico would never know the truth.
One year later, an enigmatic, 24-year-old factory worker named Mario Aburto Martinez is serving a 45-year sentence for Colosio's murder.
But otherwise, the instinctive fears expressed by the crowd have been realized: The Colosio assassination remains a mystery. It now embodies the intrigue and uncertainty of an extraordinary, historic moment in Mexico, where politics is coming to resemble a detective story.
By arresting an accused second gunman and alleging a cover-up, authorities have sketched a fascinating but unproven plot.
Emerging evidence strengthens the theory that Colosio fell victim to a political struggle in his own Institutional Revolutionary Party, or PRI, government officials say. The investigation is focusing, at least in part, on hard-line ruling party factions and suspected ties to drug cartels, an official close to the probe said.
"It points to a fight between political groups involving the cartels," the official said. "It is becoming hard to tell which field you are in, politics or drugs. This is a dangerous direction."
An unprecedented development in a separate assassination has heightened suspicions and expectations. Police last month arrested Raul Salinas de Gortari, the older brother of former President Carlos Salinas de Gortari, in the killing of the PRI's No. 2 official. Although the former president has not been implicated in that murder, critics have called for him to tell investigators all he knows about the Colosio assassination and the potential political motives and links behind the two crimes.
"Surely he has a great deal of privileged information," said Sen. Alfredo Ling Altamirano, a member of a legislative panel monitoring the Colosio probe. "It is obvious that he has information about the internal struggle. If we are talking about a political motive, this is a line of investigation. . . . There are power groups, and Carlos Salinas knows who they are and who leads them."
So far, authorities have not made public any hard evidence linking the half a dozen suspects in the Colosio assassination to each other, let alone to a mastermind. The chaos at the crime scene in the neighborhood of Lomas Taurinas has carried over into the investigations.
The latest in a string of official theories is full of ambiguities.
President Ernesto Zedillo is reportedly sure that Colosio was killed as part of a plot, and he will take the investigation as high as necessary, according to officials. But to do that, the special prosecutor, Pablo Chapa Bezanilla--the third prosecutor appointed in a year--has had to practically start over. He is reinterrogating witnesses and re-examining evidence on a trail that is now cold.
"The first phase is the crime scene," said Juan Ignacio Zavala, the attorney general's spokesman. "We are looking at the role that every one of the people around Colosio played. This takes a great deal of time. It would be risky to talk about a (mastermind) at this time."
But the investigation must go beyond street-level suspects to the elite circles where a conspiracy must have originated, critics say.
"They are still in Lomas Taurinas," the neighborhood where the assassination occurred, commented Fernando Gomez Mont, a former Baja California senator who served as a liaison between state and federal police on the Colosio case. "The special prosecutor has done good work. But he is far from completing his work. He must know that."
The hunt for a mastermind has focused on Colosio's own security commanders and, therefore, on the PRI and government.
Othon Cortez Vasquez, 28, the accused second gunman, and Fernando de la Sota--head of a shadowy campaign security unit who is now under arrest for alleged perjury in the case--had ties to Colosio's security chief, Gen. Domiro Garcia Reyes.
That alone, legislators said, makes a compelling case for also investigating Garcia Reyes, who is a member of the Estado Mayor, the military corps that protects Mexican presidents.