Oscar Perez, an officer in the country's investigative police force, addressed the gathering, urging the opposition to continue protesting.
"It's time for this narco-government to fall down," Perez said in video of the incident.
"A general walkout for July 18, walkout with no return. The zero-hour will start on Tuesday. The referendum we'll do it, with dignity, we'll be in the street defending the people."
A freelance cameraman, who asked not to be named told CNN, that he appeared "out of nowhere" at the protest, which was held to honor Venezuelans who have died in the recent unrest.
"Out of nowhere, guys with masks covering their faces called out to the media members to come and see Oscar Perez," he said.
"Oscar briefly spoke. While he was speaking, guys with masks on their faces were protecting him from the crowd. They were not letting people get close to him."
Perez spoke briefly to journalists from Univision and TVE and then hopped on a motorcycle and left, according to photographer Miguel Rodriguez, who also attended the rally.
Perez rose to prominence -- or infamy -- in June with the attack on the Ministry of Justice and the Supreme Court
The helicopter circled above the city as its occupants attacked the buildings with grenades and gunfire. No one was injured, however the attack was seen as a dramatic escalation of the months-long crisis engulfing Maduro's regime.
Perez, who disappeared after the helicopter attack incident, had previously resurfaced in a video
voicing opposition to President Nicolas Maduro.
He said that the attack on the government buildings in Caracas had gone "perfectly" to plan and that he and his associates had not meant to harm anyone.
"We had no collateral damage because that was the plan, we are not assassins," unlike, he asserted in the video, Maduro and his deputy.
Maduro condemned the attack as an attempted coup, saying "terrorists" were behind the offensive and that an operation was underway to track the perpetrators down. They remain at large.
Venezuela asked Interpol to issue a red notice for Perez in early July, according to Néstor Luis Reverol, the county's minister of interior, justice and peace.
A red notice alerts authorities in other countries, including border officials, that someone is wanted. Thursday night's rally appearance is the first time he has been filmed on the streets of Venezuela since the helicopter incident.
Descent into chaos
Soaring inflation and widespread shortages of medicines, food and other essentials have infuriated many people, who are struggling to afford even basic necessities.
Under former President Hugo Chavez, who was Maduro's mentor, oil revenue fueled Venezuela's economy. However, falling oil prices have made state subsidies unsustainable.
Anti-government protesters want Maduro to step down, accusing him of eroding democracy.
Maduro, meanwhile, has sent the Venezuelan military onto the streets to maintain order, leading to deadly clashes. At least 86 people have died in the unrest.
The government has been accused of intimidating and restricting the media, taking CNN en Español off the air. It tightly controls visas for foreign journalists including CNN, arresting those who report from inside the country without proper permits.