(CNN) -- U.N. Commandant Mark Hearns calmly takes notes on a small pad as the scene around him grows increasingly chaotic. Men talk over each other in Arabic as translators scramble to keep up. At the heart of their questions: When will the killing stop?
Hearns has no good answer.
Video of a meeting Monday between Syrian rebels and U.N. monitors in the city of Al Qusayr near the Lebanese border offers a rare glimpse of the realities of monitoring the escalating conflict.
Hearns speaks candidly in the meeting, filmed in part by journalist Robert King, expressing his own frustration and acknowledging "there is no guarantee if we answer every call that the shooting and shelling will stop."
The Syrians were complaining about the ineffectiveness of the U.N. mission as news arrived of another man shot by a sniper.
Hearns responds: "We understand and we are also very frustrated with what we cannot do."
Hearns is one of 291 U.N. military observers and more than 90 U.N. civilians currently on the ground in Syria, deployed in April to monitor the status of U.N.-Arab League envoy Kofi Annan's six-point peace plan.
Shelling and shootings have developed a pattern in the country -- while U.N. observers are in place, the shooting stops. But as soon as they leave, the violence often returns.
The United Nations for months has said more than 9,000 people have died in Syria. But death counts from opposition groups range from more than 12,000 to more than 14,000. Tens of thousands have been displaced.
CNN cannot independently confirm reports of casualties or violence from Syria because the government restricts access to foreign journalists.
"It is not the job of the monitors to stop the violence -- that is for the protagonists. But if they have the will to stop the fighting, the monitors can help them implement the commitments they make to each other and the international community. This would promote peace and stability and the conditions for a political process," Annan said last week.
At one point in Monday's roughly three-hour meeting, a rebel fighter with the Free Syrian Army pleads: "We need from you to make the Syrian government implement just one of the six-point peace plan -- move the tanks out of the city and stop the shelling."
Hearns appeared to target most of his frustration toward the Syrian government, indicating movement of U.N. monitors has been severely limited.
"The mandate or rules governing our behavior have to be agreed by everybody in including the government," he says in the video. "The point is that we have limited power but what we want to focus on is how to stop that killing, how we can make positive steps."
The U.N. official also indicated that the safety of the monitors is in doubt: "It is not safe, we will be shot at and that has been our experience. ... The government says they cannot guarantee our security."
Last month, a bomb exploded near a convoy of U.N. observers
As the delegation was preparing to leave, a young man was outside was trying to make his own point, scribbling the word "freedom" on a U.N. vehicle -- a message the U.N. commander had no choice but to take back to Damascus with him.
The brief peace went with him, too. Eyewitnesses say the shelling outside al-Qusayr resumed almost as soon as the monitors had gone.