SAN FRANCISCO (CBS SF) — Dog trainer Cornelius Austin scours the streets of Los Angeles six days a week looking for stray or neglected animals.

“I just love working with dogs and seeing dogs in a comfortable place,” Austin said.

More and more – he says he’s finding abandoned dogs – that were trained by criminals to become vicious weapons.

“I’ve seen dogs that come to the shelter, they come to my class that got scars and stuff all over their face and you know they’ve been in a battle,” Austin said.

Authorities say they’ve seen a surge of dogs used to help commit crimes…

“They’ve been used in cases of robbery, rape, assault,” Attorney Ken Phillips said.

Phillips works exclusively on cases involving dog bites. He says some felons are using dogs like these instead of guns – to avoid being sent back to jail.

“A felon is not allowed to have weapons anywhere, they know a vicious dog can be used as successfully to commit a crime as a gun or a knife,” Phillips said.

In his classes, Austin works to reverse the training some of the animals received.

He’s helped rehabilitate hundreds of aggressive dogs like a pit bull named ‘Ali.’

“He had severe dog aggression. He’s done a 180 degree turn around,” Ali’s owner Shyann Swisher said.

While he admits not every animal can be saved, he says he owes it to the dogs to try.

“If a dog could talk, he’d have a lot to tell you. Like I always tell everybody, it’s not the dog it’s the people. It’s the people,” Austin said.