Unrelenting: Marisela Escobedo Ortiz, centre, breaks down after the man, Sergio Barraza, suspected of killing her daughter Rubi Marisol in 2008 is set free. She was gunned down demanding justice for her daughter.
A mother who waged a two-year battle to bring her daughter's killer to justice was shot to death, possibly by the same man suspected of murdering her teenager.
A security video recording shows masked men pulling up in a car in front of the governor's office in the northern city of Chihuahua.
One appeared to exchange words with anti-crime crusader Marisela Escobedo Ortiz, who was holding a vigil outside.
She tried to flee by running across the street, but the gunman chased her down and shot her in the head late Thursday, said Jorge Gonzalez, special state prosecutor for crime prevention.
Ms Escobedo was taken by ambulance to a hospital, where she died within minutes.
On Friday, a group of demonstrators gathered outside the Interior Department in Mexico City to protest the killing, briefly scuffling with police while chanting 'Not one more death'.
And far to the north in Ciudad Juarez, where Ms Escobedo's 17-year-old daughter's burned and dismembered remains were found in a rubbish bin in June 2009, activists protested outside the state prosecutors office with signs demanding 'Justice for Marisela'.
Thursday's killing 'shows that in Mexico it is the victim who suffers, without protection,' veteran anti-crime activist Alejandro Marti said.
Federal intelligence sources indicated that Sergio Barraza, the main suspect in the death of Marisela Escobedo, belongs to the criminal group known as "Los Zetas", which were instrumental in the escape of Barraza at least twice in Zacatecas.
Ms Escobedo's daughter, Rubi Frayre Escobedo, disappeared in Ciudad Juarez, across from El Paso, Texas, in 2008.
After the body was discovered last year, the mother launched a campaign pressing for a conviction in the case. Ms Escobedo staged numerous marches, once wearing no clothes, wrapped only in a banner with her daughter's photograph.
'This struggle is not only for my daughter,' Ms Escobedo said through a megaphone at that march, her voice breaking. 'Let's not allow one more young woman to be killed in this city.'
Three days ago, she planted herself in front of the offices of Governor Cesar Duarte and vowed not to move until investigators showed progress in the case.
In an interview with newspapers on Sunday, Ms Escobedo said she had received many death threats from Barraza's family in which they warned that "Los Zetas" do not forgive nor forget, and that failure to abide by their rules would cost her life.
Mr Duarte said state security officials had been assigned to guard Ms Escobedo, although from a distance. He said their failure to protect her Thursday would be investigated.
Mr Duarte had also called on the state's top court to suspend the three judges.
On Friday, court president Javier Ramirez Benitez said they would be suspended pending an investigation.
Ramirez Benitez said an oversight commission found earlier this year that the case was improperly handled.
Prosecutors said Barraza, Frayre's live-in boyfriend, admitted murdering her and led police to the body. But at trial he proclaimed his innocence and claimed he had been tortured into confessing.
Grief: Relatives embrace near Escobedo's coffin before her funeral service in Ciudad Juarez
Marisela Escobedo was laid to rest on Saturday, December 18. Although the funeral was scheduled for Sunday morning, it was allegedly moved forward out of fear of her relatives becoming victims of another attack.
Shortly before Escobedo's burial a commando of at least six men busted into a nearby lumber business, kidnapped a man later identified as Manuel Monge Amparán and set the business on fire.
According to family members, the lumber yard is owned by José Monge, brother of the kidnapping victim and Escobedo's live in boyfriend.
Elements of the municipal police force stated the delinquents, before attacking the lumber yard and kidnapping Monge, had forced their way into various neighboring businesses and ordered employees to call the fire department.
"The fire at the lumber yard and the kidnapping of Manuel Monge was a retaliation by organized crime because Jose Monge refused to pay "dues," said a spokesman for the Prosecutor of Chihuahua, Carlos González.
The official denied that the attack had any connection with the killing of the activist.
Following the incident, the authorities stated the owner of the establishment had been threatened in the past, Gonzalez said.
Manuel Monge Amparán was found dead.
The Attorney General's office announced the victim, 36, was found dumped in a blanket between the streets of Mariano Vega and Ramon Alcazar.
The agency reported that the offical cause of death was asphyxiation.
Yesterday, prosecutors announced that a man's body had been found at 11:00 p.m., but the identity was not confirmed until Sunday.
His hands and feet were bound with gray duct tape and his head had been covered with a plastic bag.
Although people close to Marisela Escobedo confirmed the relationship between her and José Monge Amparán, the authorities indicated that they were no longer partners.
"José Monge Amparán, as far as we can tell from our investigations, had a relationship with Marisela Escobedo, but it was not a current relationship, it was in the past. It (the fire, kidnapping, a murder) has absolutely nothing to do, has no relation to (the murder of ) Mrs. Escobedo," said Carlos Gonzalez.