(CNN) - The death of actor Phillip Seymour Hoffman has brought attention to heroin use in the United States.
A Philadelphia DEA agent who took CNN reporter Randi Kaye on a ride-along revealed a bustling market of broad-daylight dealing. Dealers and customers were doing business on almost every street corner, and Special Agent in Charge David Dongilli explained the process of buying and selling.
"If you look at the people that just left, they're all addicts," he said, pointing out people scurrying away in run-down area of town. "They're in the neighborhood here to get their fix for the day."
The heroin is sold in tiny bags under street names like "Bud Ice," "White House," and even "DEA." The buyers were anybody from high schoolers to house wives.
Dongelli said most of the heroin on the Philadelphia streets comes from Mexican cartels. It's a cheap fix – just $10 a bag and easy to get.
The dealers have guys on the streets they call "lookouts," he explained.
"Once a buyer walks down the street, you'll have those lookouts to direct them – ‘Hey, they're on the corner of Sixth and Marshall," he said.
Lookouts keep an eye out not just for buyers, but the police as well. Some are in cars and honk their horns to alert the dealers.
When the agent's car drove by, people scattered. Dongelli said they were dealers.
Dongelli said the heroin in Philadelphia is the purest east of the Mississippi, but that hasn't stopped some dealers from mixing it with drugs like Fentanyl, a powerful narcotic often used to treat cancer patients. Just last month, 22 people died from heroin overdoses in western Pennsylvania, and all had been laced with Fentanyl.
"Fentanyl is extremely dangerous, and extremely potent," Dongelli said. "Two to three grains of salt, just to put it in perspective, could kill a seasoned heroin addict. And they don't tell you it's there," he said.
Agent Dongelli's team recently seized more than 12 kilograms of heroin worth millions on the street.
The agents also picked up multiple weapons.
Some dealers go to extremes – one woman sold heroin in McDonald's Happy Meals, police said. Buyers would come through the drive through and order a Happy Meal "with a toy." The toy cost $2, the heroin was 80 bucks more.
Those extremes make Dongelli's job harder.
"Sometimes they have small amounts on them, sometimes it'll be hidden," he said, pointing to the street dealers. "It could be hidden in that mailbox. It could be hidden under that car. It could be in that corner, then they'll go re-up the amount that they have on them. So they never take a chance to lose their product."
Copyright 2014 CNN. All rights reserved.