The massacre of three women and six children in northern Mexico made clear the fragility of Mexican government institutions and their ability to combat violence from cartels and other criminal organizations, experts told NBC News.

“What we saw was innocent victims, women and children in particular, in the crossfire or directly attacked by groups of organized criminals in a region that’s controlled by organized crime,” said Guadalupe Correa-Cabrera, a professor of policy and government at the George Mason University in Fairfax County, Virginia.

Correa-Cabrera said the killings of the nine U.S. and Mexican dual citizens, including 8-month-old twins, and the “lack of information that we have with regards to the motivation of those who committed this massacre” called into question the capacity of the Mexican government and highlighted its "fragility."

Duncan Wood, the director of the Wilson Center’s Mexico Institute, said the killings showed how vulnerable certain populations are to organized crime and the government’s inability to protect them as the country grapples with record-high murders and high-profile attacks.

“There are large portions of Mexican territory where there is an absence of the state and Mexican people, the ordinary population, are highly vulnerable,” he said.

Pressure has mounted on the Mexican government to make an arrest in the brutal highway ambush Monday. The investigation appeared back at square one after authorities said a man arrested Tuesday with a cache of weapons was not involved in the attack.

All nine of those killed lived in La Mora, an agricultural community descended from Mormon settlers, about 70 miles south of the Arizona border.

Wood said Mexican authorities “lack proper and effective investigative capacities” and because of issues in the criminal justice system, “if a suspect is actually produced, there are always going to be doubts about whether the individual or group of individuals is really responsible.”

“The justice system in Mexico remains broken,” he said.

Members of the Lebaron family mourn while they watch the burned car where part of the nine murdered members of the family were killed and burned during an gunmen ambush on Bavispe, Sonora mountains, Mexico, on Nov. 5. AFP - Getty Images

The ambush came after another incident of high-profile violence, when gunbattles erupted across the city of Culiacán in Sinaloa state last month following the capture of Ovidio Guzmán López, a son of Joaquín Guzmán Loera, the Mexican drug lord known as El Chapo. The drug lord’s son was released after police came under heavy fire from cartel fighters.

“It showed us the weakness of the Mexican state vis-a-vis organized crime, in this case, the Sinaloa cartel,” Correa-Cabrera said. “It also showed the lack of a coherent strategy to fight organized crime and the lack of coordination between the different security agencies in Mexico.”

Earlier this week, Mexican authorities said a state police officer was killed. The man did not directly participate in the operation in Culiacán, but did come in to work that day, authorities said.

Mexican President Andrés Manuel López Obrador has defended the decision to release Guzmán López, saying it was made to protect citizens and the man's capture was not worth further loss of life.

But the decision raised questions about the effectiveness of the tactic and the message it sent to organized crime, Wood said.

“Where we are right now is that the Mexican government is currently sending a message to organized criminal groups that they haven’t thought through their strategy comprehensively and they certainly haven’t defined it publicly,” he said.

A Mexican police officer inspects the scene around a bullet riddled armed forces truck, a day after gunmen and members of Mexico security forces clashed in a large gun battle in Culiacan, Mexico, on Oct. 18. Augusto Zurita / AP

Wood said the operation that captured and ultimately released El Chapo’s son was “in the heartland of the Sinaloa cartel, in the rat’s nest.”

“Planning and having adequate resources and proper intelligence should have been fundamental, critical factors,” he said. “It’s clear now those were not dealt with adequately and that’s very worrying.”

Wood said the Mexican government has been engaged in a struggle with organized crime since 2007, when former President Felipe Calderón “took the lead in addressing the problem of control of Mexican territory by organized crime groups.”

“Twelve years later, it’s tough to say we’ve had major success in reducing either the flow of drugs northwards or the hold that organized crime has over Mexican territory and Mexican society,” he said.

Wood said that the ambush this week showed “organized crime is emboldened.” While the motive of the attack remained unclear, Wood said the incident showed there were still people under a real threat of violence.

“These communities, they have signaled to the authorities they feel threatened and the Mexican government has not been able to protect them,” he said.

He added that in the recent past, organized criminal groups have stayed away from high-profile killings of U.S. citizens over the risk of response from the U.S. government. The decisions made by authorities on both sides of the border in this case could send a lesson to organized crime, he said.

“Unless there is a significant and credible response from the Mexican government in conjunction with U.S. authorities, what is the lesson that organized crime is going to take away from this?” he asked.