Mexican President Enrique Pena Nieto on Wednesday again defended the widely criticized original investigation of the 2014 disappearance of 43 students, an apparent massacre that shook confidence in his government.

In a short video released via Twitter, Pena Nieto said he remained convinced that the students from the teachers college at Ayotzinapa were killed by a drug gang and incinerated in a massive fire.

The Sept. 26, 2014, incident in Iguala, Guerrero, knocked Pena Nieto's administration off its axis after early success passing structural reforms, and it never appeared to regain balance as the country's crime rate soared.

The case was especially damaging for public confidence in officials because local police allegedly turned the students over to the gang and later investigators found that an army base in the town had been closely monitoring the situation and at best did not intervene.

International experts cast doubt on what the then-attorney general had called the "historic truth" and the students' families never accepted it. The investigation has been strongly criticized inside Mexico and abroad for the alleged use of torture to coerce confessions and failure to follow leads.

In June, a federal court ordered a new investigation into the students' disappearance that would be supervised by a truth commission. The Attorney General's Office challenged the court's decision.

"Personally, and with the pain it causes, and the sorrow it signifies for the families, I'm convinced that unfortunately it happened just like the investigation showed," Pena Nieto said.

But Pena Nieto went on to say that he will leave office unsatisfied with Mexico's security situation.

"Regrettably, at the close of this six-year term, there was a rise in criminality," he said. "We have not achieved the objective to give Mexicans peace and calm in any part of the national landscape."

Three months remain in Pena Nieto's term and he appears to be trying to give some final framing to key moments of his presidency. His party's candidate was soundly defeated in the July 1 election in what many saw as a referendum on his administration.

In another video released Tuesday, Pena Nieto defended his decision to host then-Republican nominee Donald Trump. He conceded that he had underestimated how angry Trump's candidacy had made Mexicans, but said ultimately the meeting opened a line of communication that has served Mexico.

On Monday, the U.S. and Mexico announced that they had reached a bilateral agreement that would replace the North American Free Trade Agreement. Mexican officials say they expect Canada to join as well.