DENVER -- Monday was sentencing day for a suspected serial killer. It was not for a murder charge but for a weapons violation.

Scott Kimball, 42, has been under investigation for more than a year after the disappearance of four people -- two of whom have now been found dead.

But while federal prosecutors have yet to build a case linking Kimball to those disappearances, he has been convicted of being a felon with a firearm.

Several family members of the missing showed up to Denver Federal District Court to see Kimball explain himself and hear him take the stand.

Kimball told a federal judge he knew having a hunting rifle as a convicted felon in 2006 was illegal.

"Hunting is a part of my life. Just like some people play basketball. Some people play hockey. I like to hunt," Kimball said.

Prosecutor David Conner asked Kimball to confirm that Melissa Andersen bought a Winchester .243 rifle for him at a Wal-Mart in Thornton in December 2005.

"You told Miss Anderson you were going to teach her how to hunt," said Conner.

Kimball said yes but also said he never taught her how to hunt, due to relationship trouble.

"Had I known I was going to break up with Miss Anderson there would've been no issue," Kimball said.

"You've known for years you couldn't buy a gun, that's why you had her buy it for you, right?" Conner asked.

"Yes," said Kimball. "I used it in late December 2005 and a short period of time in 2006."

Kimball was arrested after a police chase near San Diego in March 2006.

"Did you hunt after being a felon?" Conner asked.

"Yes," Kimball said. "I believe I got my first felony at 21 and I continued to hunt into 1997."

"So you're just doing that illegally?" the prosecutor asked. "Yes," Kimball said.

Kimball went so far as to ask a Division of Wildlife game warden if he needed a license to hunt coyotes at a failed cattle farm in Broomfield.

"Did you tell him, the DOW game warden, that you were a convicted felon?" Conner asked.

"I did not," Kimball answered.

"Why not?” Conner asked.

"He didn't ask me," Kimball said.

Prosecutors hope to ensure Kimball gets up to 37 months of additional prison time on the weapons possession conviction.

He is already serving 48 years on theft and forgery convictions in Boulder County.

"For so many years he got away with so much. It would be nice to see justice served," said Rob McLeod, the father of missing Kaysi McLeod. "They’re just starting to build bricks around him."

As with many other court appearances in his adult lifetime, Kimball's sentencing hearing went longer than expected, as predicted by U.S. District Court Judge Marcia Krieger.

"It would appear the amount of time scheduled for this hearing would be inadequate. There is no way we can complete this in 45 minutes," Judge Krieger said.

The hearing will continue June 9.

For his ex-wife it was an unusual day.

"I got sick to my stomach. I can't tell you when the last time I saw him might've been," said Kimball's ex-wife, who did not want her name used. "He hasn't changed. He has not changed for the last 20-something odd years. He's aged. He always implied that he was far more intelligent than anyone."

The two were married from 1993 to 1997, she said.

She believes the two boys she shares with Kimball may've been the reason he came to Colorado, requesting a prison transfer to be closer to them.

"They miss their Dad terribly. He was always the 'fun uncle', so to speak," she said.

The teenagers will ask about Kimball occasionally but she said she'll tell them the whole story when they're old enough to have a beer with her.

The case may still be unfolding even then.

Used as an FBI informant in 2002, Kimball was close to four Colorado people who all disappeared between 2003 and 2004: Kaysi McLeod, Leann Emry, Jennifer Marcum and his own uncle, Terry Kimball.

The remains of Emry and McLeod have been found; Emry in Utah and McLeod in Jackson County, Colo.

Earlier this spring, Kimball was brought back out to the same area of western Utah where Emry was found in March in order to search for Marcum.

Sources close to the investigation said it was not successful.

A family member of Kimball's even claimed there were some disagreements among federal and local officials.

"There is no tension between our office and the FBI. We have been working very hard together to solve the cases we have been working on,” said Sheriff James D. Nyland, of Grand County, Utah.

It was McLeod and Bob Marcum, Jennifer's father, who convinced the FBI to take a closer look at Kimball in the missing persons cases.

"He's got a photographic memory. He knows exactly where she's at (Marcum). That's what I believe. I think this thing's got another year or two before it plays out. It's been six years already. You can be patient when you have no choice," McLeod said.