Updated at 7:15 p.m. Friday with comments from the veteran's daughter and the U.S. attorney's office.

A gun collector and decorated Vietnam veteran from Plano was hailed as an "American hero" by some — before his private arsenal and an illegal drug habit landed him in prison last week.

Federal authorities and Alfred Pick's daughter portrayed the 70-year-old retired Army lieutenant as a mentally unstable addict who ultimately led those closest to him to fear for his and their own safety.

Alfred Pick was photographed in 2001 for a story about his subdivision beside an airstrip in Plano. (Staff photo)

"I didn't want to be the person who knew he was a danger and didn't do anything," said Pick's daughter, Amber Zable, who reported him to federal authorities. "I felt really conflicted about basically betraying my dad, but this person was a danger and a menace."

A year after federal agents raided Pick's home, U.S. Attorney Joseph Brown announced that a federal judge had slapped the decorated Vietnam veteran with a seven-year sentence for owning a firearm while illegally using controlled substances.

Agents with the Bureau of Alcohol, Tobacco and Firearms also found Pick to be in possession of cocaine and marijuana, according to his indictment. He pleaded guilty to the charge in April in a deal with federal prosecutors.

When Pick came across a rare M14 rifle decades ago at a Fort Worth gun show, his lawyer says, it reminded him of the weapon he'd carried in Vietnam.

"It was probably the piece de resistance of his collection," Mark Shackelford told KTVT-TV (CBS 11). "He had shown it to me. I've never seen it taken out of the case."

In addition to being a gun collector, Alfred Pick flies airplanes and was the subject of a 2001 story about his Plano subdivision next to an airstrip. (Staff photo)

Pick said he had come across the rifle at a gun show in the early 1980s. The serial number had been scratched out, he said — which some fellow vets note should have been a red flag.

Still, "it was rare to see one, so he instantly had a connection to it," said Pick's attorney, Ryne Sandel. Pick ultimately accumulated over a dozen weapons, many of them collectibles, the attorney said.

Four decades ago, according to CBS 11, after more than 100 combat missions and what the station said was a brief time as a prisoner of war, Pick was awarded the Silver Star.

But last year, the station reported, two weeks after his wife of four decades died, the ATF raided Pick's home and found the M14, along with a collection of 13 other weapons. He was sentenced to 87 months in federal prison.

"He's had it all these years, never robbed a bank or done anything with it," Shackelford said. "I would think that when a man turned 70 and is an American hero, you don't destroy the rest of his life for one mistake."

But in court, prosecutors presented a much different story, saying that Pick had admitted to others that he had stolen the illegal weapon while in the military. They also recounted how in October 2017, Plano police had been called to a local hospital regarding "a belligerent individual."

There, officers encountered Pick, who, upset about his wife's treatment in the hospital, told medical staff and others that he would return with a gun and "shoot [them] in their kneecaps and elbows first and let them bleed."

Police took Pick into custody and delivered him to mental health authorities for evaluation.

Pick's daughter told The Dallas Morning News that her father's mental health had increasingly deteriorated as he cared for her terminally ill stepmother, who she said suffered from a rare, degenerative neurological disease.

"He started to become hopeless and frustrated," Zable said. "Being the primary caregiver for someone who is not going to get better is very emotionally, physically, mentally and financially taxing. It really started to wear on him."

Her father's longtime drug use, she said, became even more problematic.

After her stepmother died, Zable and her husband began going through her father's property as they tried to sort out the deceased woman's affairs, and they were alarmed by the amount of drugs and weapons in the home. That's when they decided to call federal authorities.

The ATF found more than 2 grams of cocaine, more than 10 grams of marijuana and 14 firearms at Pick's home, including the one with the obliterated serial number.

Prosecutors also informed the court that Pick had been repeatedly cited for criminal trespass at area hospitals for his aggressive behavior and that police had twice been called in 2014 to defuse situations in which Pick had brandished handguns and threatened others.

In exchange for Pick's guilty plea to the charge for which he was convicted, two other charges were dismissed: possession of an unregistered firearm and possession of a firearm with an obliterated serial number.

"Obviously, there was a lot more to the sentence that was received — a sentence that Mr. Pick and his lawyer agreed to — than a single gun with a missing serial number," said Brown, the U.S. attorney. "Although Mr. Pick was a decorated veteran, he would use that status routinely to try to excuse his repeated criminal behavior. This was also not a mental health issue. It became a public safety issue."

CORRECTION, 6:45 p.m. Oct. 19, 2018: A previous version of this story did not clarify that Alfred Pick was convicted for possessing a firearm while using illegal drugs. It also mistakenly said he lost his wife to cancer. She died from a neurological disease.