Activists in the southern Mexican city of Oaxaca have handed over to police four people they took hostage for 18 hours amid continued political tension.
Oaxaca has seen increased violence in recent weeks
The crisis began when a man was shot dead on Thursday during a march by striking teachers who are demanding the resignation of Oaxaca's state governor.
The activists seized the four, accusing them of involvement in the man's death.
Oaxaca's teachers have been on strike for weeks to call for more pay and for Governor Ulises Ruiz to step down.
Protesters accuse Mr Ruiz of rigging the 2004 election to gain office and of using force to suppress dissent.
The dead man was identified as 50-year-old Jose Jimenez but the circumstances of his killing are unclear.
Protesters said gunmen had opened fire without provocation as several thousand teachers marched through Oaxaca.
But the state prosecutor said initial investigations indicated he was shot during an argument.
Activists from the Oaxaca People's Assembly, which organised Thursday's march, seized four people who they accused of being involved in the killing and took them to a local television station which their group took over several weeks ago.
Historic Oaxaca is one of Mexico's main tourist centres
A house where the bullets where believed to have come from was set on fire by the protesters.
The activists subsequently handed over the four to the authorities, saying they hoped there would be a full investigation.
The protesters have blamed Governor Ulises Ruiz for the attack, a charge his office rejected.
The governor condemned the violence.
About 300 people held a funeral ceremony for Mr Jimenez on Friday, carrying his coffin through the city streets.
The city has seen continuing protests since June, after police attacked a teachers' rally.
About 2,000 people have been camping out in the centre of the city, where they have set up barricades and smashed windows.