Editor's note: CNN's Moni Basu followed Sean Penn in Haiti on May 4, documenting the celebrity's life as an aid worker, including his efforts to save a boy with diphtheria.

Port-au-Prince, Haiti (CNN) -- At base camp, Sean Penn sits under a lampshade made with discarded Chef Boyardee packages and pulls closer a Bic lighter dangling from a rope.

It's not quite 7 a.m. and Penn is smoking another Marlboro Light. He brought Nicorettes with him to Haiti, but quickly gave up on the idea of refraining from cigarettes.

He runs his hands through disheveled hair, takes another drag. Wrapped in an embossed white towel and barefoot, he says no hellos, makes no attempt at niceties.

He starts telling a harrowing tale from the day before.

He hunted every corner of Port-au-Prince for an antitoxin for Oriel, a 15-year-old boy who contracted diphtheria, an acutely infectious disease spread through respiratory droplets.

The American Red Cross didn't have it. Nor did any of the major hospitals. Penn even had the U.S. military on the search.

The United States stockpiles the vaccine and antitoxin. But in Haiti, it took Penn -- even with his star power -- 11 hours to get his hands on one dose.

It was at a medical warehouse and Penn wrested the head of the World Health Organization from bed to unlock the door at a late hour.

"This country is not ready for an emergency," he says.

"Three months in and nobody in the major hospitals knew where to find the immunoglobulin. That kinda says it all to me."

Oriel had been brought to a clinic at the encampment of earthquake-displaced people at the Petionville Golf Club, which Penn's newly formed aid agency J/P Haitian Relief Organization has been helping to manage.

The boy had started feeling symptoms six days earlier. Doctors quickly realized that he had diphtheria. No hospital wanted to admit the boy, Penn says. They did not have the capacity to prevent infection. Penn hand- carried him to General Hospital, the city's main medical care facility, where doctors finally agreed to place Oriel on life support.

Penn feels personally responsible -- for the boy, for the entire camp, for the city. Diphtheria could spread lightning fast through the congested tents and shanties.

Haiti grapples with diphtheria and other killer diseases every year, but after the quake doctors feared the worst. Oriel was the first case of "the worst" discovered at the golf course camp.

Early on, the Centers for Disease Control and Prevention had urged immediate vaccination against diphtheria and recommended having the antitoxin on hand.

Penn cannot comprehend why, with an abundance of aid agencies working in Haiti, prevention like this has to be so difficult. He is not one to shield his anger, or mince words. "If the boy were to die," he says, "this would be murder."

Celebrity in a foreign land

Penn is hardly new to heroic endeavors. He's flown to the eye of a hurricane, to the front lines of war. A few years back, he traveled to Iraq and Iran and wrote about both countries for the San Francisco Chronicle.

He was in New Orleans after Hurricane Katrina -- his right arm bears a tattoo that says: "NOLA, Deliver Me."

His presence in all those places and now in Haiti draws skepticism and ire from those who think that celebrities use tragedies to burnish their public images. Penn has been mocked and caricatured by filmmakers, writers and talk-show hosts for taking up causes.

But he brushes it all aside. Someone, he says, has to get it done.

He landed in Haiti a week after the earthquake, he says, with a genuine concern. He insists he will be here for the long haul, that he's more than a celebrity goodwill ambassador who has dropped in to smile with orphaned kids for a day.

No stunts. No gimmicks. His staffers say the actor is simply following his heart.

The Oscar-winning star has shed his life of comfort and glamour for the unassuming role of aid worker. For the past few weeks he has been helping manage 50,000 displaced Haitians living in the camp that sprouted on the nine-hole course at the capital's once-exclusive golf club.

Perched atop a hill that affords a view of Port-au-Prince, the star of movies like "Dead Man Walking," "Mystic River" and "Milk" might have been a guest here in former years, sipping a rum punch on a balmy evening. These days, he's sleeping in a tent along with a small proletarian staff. They wear navy blue shirts with the J/P HRO logo loudly emblazoned -- and answer only to Penn. Void of the bureaucracy common at the United Nations and other major humanitarian agencies, Penn says his J/P HRO, is often able to get things done faster.

The group's work began in the weeks after the quake with the disbursal of critically needed aid. Then Penn noticed the tremendous need at the crowded golf club camp, one of the city's largest and completely vulnerable to rain and treacherous mudslides.

Penn called in the U.S. Army's 82nd Airborne Division to help secure the hills with gravel and sandbags.

"Pretty soon, we were managing a camp," he says. "Then you find you are filling a gap and you feel responsibility to keep going."

He negotiates the terrain in a bright red golf cart that says "SEAN PENN" in the front, though few recognized him when he first arrived. Even now, some camp residents barely recognize the name.

"Yes, I know," said one. "He is Madonna's first husband."

Penn, who will turn 50 this year, found it liberating to move without paparazzi or fans asking for autographs.

It was the anonymity he once knew growing up in southern California, before his breakthrough role in the 1983 film "Fast Times at Ridgemont High."

Then came his turbulent marriage to Madonna, a barrage of bad tabloid headlines and jail time for punching an extra who tried to snap his picture.

Learn more about Haiti relief efforts on "Impact Your World"

But he's no bad boy here at the Petionville Golf Club.

"He is helping us. He is a good man," says camp resident Junior Vital.

Penn's group relocated about 5,000 people to safer ground at Corail, a new temporary camp on the outskirts of the city, where flooding and mud will not threaten them in the rainy season.

In the landscape of Haiti's tragedy, Penn's accomplishments are small. But things don't happen quickly here.

In that context, aid workers here gave him kudos for his successes.

"It was a Band-Aid measure," Penn says. "But it meant a lot to us."

Still, he recognizes he's a newbie to the aid business. And a possible diphtheria outbreak is not the kind of emergency the Hollywood actor is used to addressing.

Foul mouth can undo good intentions

Penn shaves at an outdoor sink, takes a quick shower.

J/P HRO's medical director, Justine Crowley, takes a call from the hospital. The teenage boy with diphtheria is not doing well. Now that he is intubated, doctors from the International Medical Corps are concerned that infection can spread. The walls of the hospital's rooms do not go all the way up to the ceiling; not everyone at General is vaccinated.

They are also miffed at Penn, whose foul mouth and abrasive manner can undermine his good intentions. Penn decides to pay a visit to the hospital to sort out matters. He asks staffer Stephen Duvall if he can borrow a button-down shirt. Duvall gives him the one off his back.

"The main thing is to make sure they will keep him here and treat him," Penn says to Crowley.

He asks the driver for a light, smokes another Marlboro Light and sings a song by the politically charged rock band The Clash. "This is Radio Clash on private satellite."

"That's what we need -- a pirated radio station," he says. "No, no. I don't mean pirated."

Penn sees a lack of communication and coordination as a big problem in aid delivery to Haiti.

He sees some aid workers as having been in the business too long. "Dispassionate," he calls them. Others bask in the glory of their achievements.

He sees it as a clique -- one that hasn't let him in yet.

What do they, in turn, think of him?

Several aid workers who were asked about Penn's contributions in Haiti did not want to be quoted. Most said the actor was doing more good than harm. "He has money and an organization," says Mark Turner, spokesman for the International Organization for Migration (IOM). "He's done a very credible job."

If nothing else, aid workers say, Penn's celebrity helps keep the spotlight on Haiti.

At the hospital, Penn meets rankled doctors. They discuss the boy and the fact that he had been going to school, which means other students might have been infected.

After settling on a game plan, Penn rushes out to a morning meeting of camp managers at the U.N. logistical base.

A German missionary accosts him on the street.

"You are Sean Penn?" says Kolja Witt. "I think you are doing good work."

A group of Haitians working with International Medical Corps want their pictures taken with the Hollywood star.

Penn obliges. Smiles, even, for the camera.

"You, Sean Penn. Excuse me," says another man. "My name is James. Can you help me get a job?"

Penn explains he cannot help him and jumps back into his white Toyota Land Cruiser. It pulls away but Penn is still very much at the hospital.

"He's not going to die," Penn says of the boy. "He's his father's only child. That's not allowed."

He pauses before finishing the thought. "But that's a brand new law around here."

At the U.N. logistical base, a spread of trailers and tents erected near the airport after the headquarters building collapsed in the quake, Penn heads to the Deck Bar and Grill.

Ham panini and soda in hand, he walks into a weekly meeting of camp managers at the IOM.

It's new for Penn to sit through metrics and charts and aid-worker speak. He doesn't have much patience for priority lists aid agencies want made. He just wants things done now. The room is packed; it's hard to hear speakers in the back. But not Penn. His voice is booming. His language is not pedantic.

The discussion centers on assistance packages for quake-displaced Haitians living in makeshift camps.

Penn disagrees that the aid amount should be a uniform $50 per person -- because needs vary -- and until the parameters are worked out, no one gets anything.

"If you have a hospital with some medicines, you start treating the patients. You don't wait for the shelves to be full," he says.

Penn brings up the diphtheria case. He wants aid agencies to begin immediate vaccinations. UNICEF has plans to do just that, but has not started yet.

He says Oriel is suffering needlessly. He doesn't want to point fingers but in his mind, he blames inertia on the part of humanitarians who should be acting faster, more efficiently.

He doesn't want to hear that they are experts from Africa and that he is just a Hollywood actor.

He just wants them to act.

A boy's death, an angry activist

In the end, Penn's efforts to save Oriel were not enough. He had been sick for six days before receiving treatment. He died Thursday night. The child's death, Penn says, was needless; one that could easily have been prevented.

Even in Haiti.

Penn has already started chastising the international community. Where are the vaccines? Where is the prevention?

There won't be a rebuilding of Haiti without its people, he says. Saving their lives must be the top priority -- before jobs, before reconstruction, before anything else.

"We've got to get people out of these ad hoc camps where these kinds of diseases can spread so quickly," he tells Anderson Cooper.

Watch Penn discuss diphtheria on "Anderson Cooper 360"

Penn thinks of his own children often. They've been down to visit him in Port-au-Prince.

He had said Oriel's death would not be allowed. But Penn didn't have it his way this time.

There are no retakes. And in his mind, no excuses.