Gun sales in the United States have soared in recent years. According to statistics compiled by the FBI, background checks for gun purchases jumped to nearly 13 million last year, up from 8.9 million in 2005.
This year the FBI is on pace to process a record 16 million background checks for gun purchases. Most of the sales are to law-abiding citizens. But criminals are in the market, too, say experts.
Some of the methods the criminals use to illegally obtain guns are surprising, including walking right into to a gun store and buying them.
In Long Beach, Calif., a surveillance video obtained by ABC News shows a gun store clerk making an illegal handgun sale, police say. The clerk was secretly recorded by an ATF informant and a female undercover agent.
In the video, the clerk is told that the man who wants to buy the gun is a convicted felon, making the sale of a firearm illegal. It is illegal for convicted felons to own guns anywhere in the US.
"I like this one," the undercover agent says, pointing to one of the guns. "Its $200," says the clerk.
The ATF informant and undercover agent then devise what's called a "straw" purchase scam where the man posing as a felon has his girlfriend buy the gun. The whole process – which is also illegal - takes less than two minutes.
"What about her; can she do it," the informant asks, pointing to the other undercover agent who is a woman. "She can do it," the clerk says.
The straw purchase scam is one of the primary ways criminals get guns, according to law enforcement officials.
In the last five years, ATF has arrested more than 6,000 people for participating in such scams. It's even easier when the gun dealer is aware of the deal. Since 2006 ATF has identified more than 700 instances where dealers sold guns to people they suspected of being banned including felons, fugitives, and the mentally ill.
"It is big business," says Mark Kraft, a senior ATF official. "In the same way that people traffic drugs, people traffic guns."
Authorities say the overwhelming majority of the nation's more than 100,000 gun dealers are legitimate. Yet when even one dealer goes rogue it can have deadly consequences.
In New Orleans, three employees of a gun shop were sent to prison last year for diverting guns to criminals. Police say guns from the store were involved in up in 127 murders and more than 500 drug-related crimes.
Guns from dirty dealers flow into a thriving black market where thousands of weapons change hands, say law enforcement authorities.
Police in Pennsylvania caught an illegal gun peddler on surveillance tape showing off his weapons to two men he believes are convicted felons. They're really undercover agents.
"How much was that shot gun?" the undercover agent is heard asking. "$350 for a Smith & Wesson," the clerk is seen saying. "Can we do the four for $1900?" the agent asks. "Just give me $1850," says the clerk.
In America, getting guns illegally is usually just that easy, say police.