In Englewood, Colorado, thousands of patients go to the Swedish Medical Center every year to be treated for illnesses. But now that same hospital is warning patients they could have been exposed to several deadly diseases, including HIV.

Rocky Allen, 28, has worked as a surgical technician for years, but his face is probably the last one you'd want to see if you were on the operating table.

Margaret Wegrzyn was a patient at Swedish Medical Center in Denver. She remembers Allen, not only because he came back three times to administer narcotics to ease her pain, but she also remembers that nothing happened.

"I said 'What did you give me? You know, it's not working,'" said Wegrzyn.

That's because Allen allegedly took the drugs himself, shooting up the powerful narcotic fentanyl, then replacing the syringe and using it, allegedly filled with saline, on Wegrzyn.

Wegrzyn is one of thousands of patients who may have been exposed to hepatitis and HIV.

At this point officials have not said if Allen has tested positive for any of these diseases, but patients are stressed because anytime a substance abuser randomly swaps needles, it puts others at risk.

Allen is a Navy veteran with a glowing resume, having worked in two Naval hospitals as a medical worker in Afghanistan, Iraq and Kuwait.

But he seems to have led a double life. After the accusations surfaced the hospital fired him.

Documents allege Allen has a long history of substance abuse that somehow never prevented him from finding work.

The tech jumped from hospital to hospital and crossed state lines.

His first stop: Scripps Green Hospital in San Diego, where he worked for only 20 days before he got the ax.

"Another operating room employee witnessed him attempting to switch fentanyl, the pain medication, for saline," said Scripps spokesman Don Stanziano.

A statement from the manager of patient care reveals details about her meeting with Allen following the allegations: "You were observed watching the doctor and when he turned his back to draw up medication ... you were seen switching syringes and taking the syringe from the cart and placing it in your scrub pants. You were asked what you planned on doing with the syringe of fentanyl ... You said you were going to inject it."

After his short San Diego stint, Allen worked at two Arizona hospitals where he was fired after testing positive for drugs.

That's when he moved to Denver, where allegedly his disciplinary employment history went undetected.

Now patients are lawyering up, and they want answers.

Attorney James Avery represents 14 patients, including two who have tested positive for hepatitis. He says Swedish Medical Center didn't follow protocol.

"The surgical technologist was administering drugs to the patient, which is clearly forbidden by the Colorado statute," said Avery.

The feds busted Allen, charging him with tampering and obtaining a controlled substance by deceit. Allen pleaded not guilty.

For now, close to 3,000 potential victims will be given free blood screenings, but it will take weeks for the results to come in.

Allen's trial is scheduled for April.

Until then he's free on bond. The judge is requiring him to stay in a halfway house, submit to drug testing, and perhaps the most important, find a job out of the medical field.