As Coptic Christians mourned the death of protesters slain by security forces, Egypt’s military leaders faced unprecedented public anger Monday and growing doubt about their ability to oversee a promised transition to democracy.

Government officials vowed to investigate the causes of the worst violence since President Hosni Mubarak’s ouster in February. But a growing body of evidence, including video footage and witness reports, suggest that military forces opened fire on unarmed protesters and deliberately drove hulking armored vehicles into crowds of civilians.

Muslims and Christians who attended a funeral for the victims of Sunday night’s crackdown chanted angrily for the dismissal of the country’s military chief, Field Marshal Mohammed Hussein Tantawi.

The bloodshed, in which at least 25 people were killed and more than 300 wounded, marked the most powerful blow to the military’s image as the protector of the revolution, a status it earned by showing restraint in the face of a popular uprising.

Since it assumed control of Egypt on Feb. 11, the military has been criticized for governing erratically and failing to uphold the democratic principles that fueled the revolution. Soldiers have been accused of using excessive force in some instances and of failing to intervene in others.

“The army realizes that its forces committed a massacre against a religious minority,” said Hossam Bahgat, head of the Egyptian Initiative for Personal Rights. “There is no telling what will follow.”

Perhaps the most troubling lesson from Sunday’s unrest was the ease with which simmering sectarian tensions and a mob mentality could unleash chaos in a country ruled for decades as a police state.

That dynamic poses a dilemma for the military leadership, which must balance its desire to maintain stability with a pledge to oversee a transition to democracy. Some observers fear that commanders could use the rising tension as a pretext to delay the shift to civilian rule and rely more heavily on authoritarian tactics.

Sunday’s events, and other recent steps by the military, including its indecision on the electoral process, show that its leaders are still learning how to govern, said Adel Iskandar, an Egyptian American who teaches communications and contemporary Arab studies at Georgetown University. “A lot of people believe that this is the second phase of the revolution, and the next institution to be confronted is the military.”

‘Hidden hands’

Prime Minister Essam Sharaf said the violence was a further setback to what the country’s leaders had acknowledged has been a difficult transition to democracy. In a televised address late Sunday, he blamed the unrest on “hidden hands, domestic and foreign,” resorting to a line Egypt’s interim rulers have used in recent months to try to absolve themselves of roles in the country’s woes.

The military council said Monday that it would not allow a rift between the military and the people to grow. It said it would form a committee to investigate the incident and take the “necessary precautions to stabilize security,” and it promised to hand over power to a civilian government. The statement appeared to be a response to critics who accused the military of using the violence as an excuse to prolong its rule.

The White House said Monday that President Obama was concerned about the violence. As Egypt moves toward civilian rule, “the rights of minorities — including Copts — must be respected,” said press secretary Jay Carney, adding that the clashes “should not stand in the way of timely elections and a continued transition to democracy that is peaceful, just and inclusive.”

But in the Coptic Christian cathedral in the Abbasiya district of the capital, where the funeral was held Monday afternoon, anger and dismay were palpable.

A woman who lost her fiance collapsed in grief. A father wept as he reached for his son’s coffin as pallbearers carried it down the aisle. Bloodied clothes were passed through the crowd as thousands cried, condemned the military and called on God for help.

One man cursed the military as others tried to subdue him.

“Oh, martyrs, sleep and rest, we will continue the struggle,” mourners cried out in chants that echoed through the packed cathedral.

‘No more tolerance’

Copts, who make up roughly 10 percent of the population, said the crackdown exacerbated the feeling that they are second-class citizens — a sentiment held before and after Egypt’s revolution.

Mubarak’s regime protected Christian churches and brutally clamped down on fundamental Islamist groups, keeping religious tensions subdued. Sunday’s unrest, coming after recent attacks on churches, underscored the Copts’ vulnerability.

“We are persecuted by the state,” said Sila Abd al Nour, a Coptic priest. “Islamists attacked us, and the army did nothing. They ran us over with their vehicles and shot at us.”

State television, controlled by Egypt’s military rulers, also came under fire Monday for coverage that activists and human rights workers said incited violence. Broadcasters called on “honest Egyptians” to take to the streets to defend the military from what anchors described as Coptic Christian assailants, a call that appeared to resonate with Egyptians who thronged downtown wielding clubs and chanting pro-Islamic slogans.

Mina Daniel, 25, a well-known blogger and Coptic activist, was shot twice during the wintertime revolt but survived and returned to Tahrir Square, the epicenter of Egypt’s revolution. But Sunday, he was shot in the chest and bled to death, according to his death certificate.

“This time, the military put him to rest forever and by force,” said Ola Shahba, a friend and a Muslim. “There is no more tolerance for the military, and we need to stand together against them. It’s something we’re all willing to die for.”

On Monday night, Coptic Egyptians and Muslims marched together from the cathedral to the hospitals where the dead had been treated. When they heard gunfire in the distance, some chipped away at the pavement to gather stones to defend themselves.

“Tantawi is a racist and a coward,” they chanted as they called for revenge. “They killed the Copts by bullets.”

Hassieb is a special correspondent. Correspondent Ernesto Londoño contributed to this report.