RACHEL MARTIN, HOST:

Twenty years ago today, shots rang out in a poor neighborhood in Tijuana. That sound reverberated throughout Mexico. The victim was the man hand-picked by the country's dominant ruling party to win the country's presidential election. The crime and its unanswered questions weakened that party's standing and would mark a catastrophic year for Mexico.

NPR's Carrie Kahn looks back at a killing that was similar to the assassination of John F. Kennedy, in that it shook a country to its core.

CARRIE KAHN, BYLINE: Like Kennedy's assassination, the murder of Luis Donaldo Colosio had a lone gunman, countless conspiracy theories and a grainy video.

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KAHN: Filmed from behind the crowd in a campaign rally in Tijuana, Colosio is easily spotted by his curly hair. Loud Norteno music blares as he's jostled by the crowd. Suddenly, a black pistol emerges just above the candidate's right ear, then fires.

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KAHN: The crowd screams. The bloodied candidate is lifted out of the dust and rushed to a nearby hospital. The crowd sets upon the gunman, beating him until he's thrown into a car and whisked away.

DENISE DRESSER: It was an event that put the country in a state of chaos, of uncertainty. It marked the beginning of the year of living dangerously, 1994.

KAHN: Denise Dresser, a political analyst, says 1994 was supposed to be Mexico's moment. The North American Free Trade Agreement took off and the country waited for its promised prosperity. Instead, the year started with an armed Zapatista uprising in the south. Colosio was then shot in March, foreign capital fled and by year's end the Mexican economy collapsed.

DRESSER: Expectations that everyone had at the time about Mexico heading towards the first world and then realizing that with that assassination and its consequences and its ripple effects, that was not going to be the case.

KAHN: For one, the assassination would create cracks in the iron grip the Institutional Revolutionary Party, or PRI, had held on Mexico for the past 65 years. First, the party tried to pin the blame on Ernesto Ruffo Appel the opposition governor in Baja California, home to Tijuana.

ERNESTO RUFFO APPEL: (Foreign language spoken)

KAHN: Ruffo recalls Mexico's attorney general at the time storming into his office and saying you did it. Your people did this. Stunned, Ruffo reminded the attorney general that it was the local PRI party that had taken control of Colosio's security that day. Quickly, attention shifted to that security detail - former state police officers, some with dubious backgrounds. That was one of many suspicious turns that dominated the investigation and fueled accusations all the way through the PRI party ranks up to then-President Carlos Salinas. Dora Elena Cortes, a longtime Tijuana reporter, says a parade of incompetent special prosecutors did little to curb the speculation.

DORA ELENA CORTES: (Foreign language spoken)

KAHN: Cortes says investigators never followed up on crucial evidence or interviewed key witnesses. Only one person remains jailed for the murder - Mario Aburto, a local factory worker who says he committed the crime to call attention to his pacifistic beliefs. But Cortes says evidence of a possible second gunman was overwhelming. Colosio was shot twice in the head and in the stomach, yet only one bullet was ever recovered. A doctor told reporters his death was caused by two bullets of different calibers. A federal agent in a bloody shirt and gunpowder residue on his hands was arrested at the scene and later set free. One man was ultimately accused of being the second gunman and arrested a year after the crime.

OTHON CORTEZ: (Foreign language spoken)

KAHN: Othon Cortez, a PRI Party chauffeur, says he was tortured and imprisoned for two years. Ultimately, he was freed for lack of evidence.

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KAHN: Cortez, who now works at Tijuana's zoo, says Mexico's judicial system remains as flawed as it was 20 years ago and no one believes a lone gunman killed Colosio. Two decades later, many in Mexico still wait for justice to be served. Carrie Kahn, NPR News, Tijuana.

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