Downtown Austin has become a concrete jungle where drug dealers prey on the homeless.

"They're emboldened because they think they have the perfect victims," said Austin Police Commander Troy Officer.

It’s a disturbing discovery Austin police made in Operation SPERO, a month-long sting to stop drug activity around the Austin Resource Center for the Homeless, or ARCH.

"They're not homeless people. They don't use the resources downtown,” Officer emphasized. “They are simply predators who come downtown to prey on our most vulnerable population, which is our homeless."

Undercover officers caught 81 people selling drugs there; one of them was only 16-years-old.

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"Never has there been one so big that 81 people are now facing prison time," exclaimed Assistant Police Chief Justin Newsom.

Austin police have been keeping an eye on the ARCH for a while and they have done several drug operations in that area. But with Operation SPERO, police also worked with homeless advocates.

"We need this partnership with APD,” said Ending Community Homelessness Coalition’s Ann Howard. “We need to know that we're not criminalizing homelessness, but that we're looking out for the people who are homeless."

Advocates say people who work with the homeless are also worried about their safety downtown.

"We have a lot of our residents and people who come to us for meals who have expressed to us how fearful it is for them in the streets," Salvation Army Major Andrew Kelly said.

Now that these 81 people are off the streets, it gives them some peace of mind; but the work is just getting started.

"As you move the sharks out, new sharks move in and that's probably the best analogy I can use,” Officer said. “So, I think this will have a short term impact."

"This is a long-term operation and this is just one front,” he added. “We clear the way so that these folks can perform the services that truly make a difference."

Investigators say all exchanges were caught on camera and all of those arrested face drug distribution charges.