Seven Venezuelan military officers were killed on Saturday when their helicopter crashed while heading to a state where President Nicolás Maduro appeared alongside troops, days after the opposition called in vain for a military uprising.

The Cougar helicopter hurtled into a mountain outside Caracas in the early hours of an overcast day in the capital. An investigation was underway.

The armed forces in a statement said the chopper was heading to San Carlos in Cojedes state. That’s near a military academy where Maduro appeared early Saturday to oversee training exercises following a week of intrigue that saw a small group of security forces turn against him in the failed attempt by opposition leader Juan Guaidó to overthrow the government. On board the helicopter were two lieutenant colonels as well as five lower-ranking officers. The statement didn’t say if the chopper was part of the presidential delegation.

Also in Caracas on Saturday, a protester handed over a written appeal for the military’s support, but a Venezuelan policeman burned the document and let the ashes fall to

the ground. The armed forces “won’t be blackmailed or bought,” said a second officer standing nearby.

Benito Rodriguez fumed as he watched the events unfold.

“It’s a humiliation,” said Rodriguez, a demonstrator who had joined a crowd of about 150 protesters gathered near La Casona, a residence historically used by Venezuelan presidents. The scene highlights the uphill battle now facing opponents of Maduro who have failed to persuade the country’s security forces to join efforts to oust the leader.