Heineman said that clients were crying and upset inside and that they don’t believe the veterinarian they call Dr. Lou would do the things he’s been accused of doing. They say they’ve brought more than a half dozen animals to the clinic, some of which have had to be euthanized over the years.

“We don't believe for one second that he's done anything unethical,” Heineman said.

Heineman believes there may be ulterior motives to some of the complaints that have come to light this week. He says there have been thousands of clients over the years who haven’t had any problems. He and his son are hopeful the doctor’s license is re-instated.

“The community and his patients and clients will lose dramatically by not having him practice as a veterinarian,” Heineman said.

Numerous other clients told NBC News the same thing.

“I’m kind of heartbroken. Whoever is in charge needs to figure this out real quickly,” said Ben Abramowitz. “We need to have him here practicing medicine and not dealing with this kind of harassment.”

One of Dr. Tierce's many supporters who turned up at his clinic Thursday acknowledged to NBC News that the details of the arrest warrant are ugly.

"[If] that's all you’re gonna see, you're gonna see that he’s a quack and a freak and an evil person and a vampire,” said Sandy Kurtzman, who has been a satisfied client of the Camp Bowie Animal Clinic and Dr. Tierce for nearly two decades.  “You're not gonna get the whole story about who Dr. Lou Tierce is. There's a reason why I call him 'Saint Lou.'"

To back up her argument, Kurtzman brought with her Marley, her neighbor's Labrador. Marley had been run over by a car last spring, and other veterinarians had recommended one of his legs be amputated.

Instead, according to Kurtzman, Dr. Tierce operated for nine hours that night, implanted a pin and rods in his joint, kept Marley in the clinic for several months while he healed, and only charged $3,000 for what he said was easily $10,000 in care.

Another, more recent client of the Camp Bowie Animal Clinic, said he only learned on Thursday about the accusations and the criminal charge against his dog's new vet.

Cary Powers, of Southlake, told NBC News he brought his very sick akita, Kiera, to Dr. Tierce upon the recommendation of his regular veterinarian who told him that Dr. Tierce may be able to help.

Late Tuesday night, hours after Fort Worth police and state investigators raided Dr. Tierce's clinic, the vet called Powers shortly after 11 p.m. and again after midnight to provide grim updates that Kiera may not survive. And not once did Dr. Tierce mention the legal trouble he was facing.

“I think that says a lot for a vet that he put the time in, especially on the day when your whole life seems to be falling apart,” Powers said.