Joe Keller, 19, was last seen on July 23 running in a remote area of Colorado.

You can hear the gloom in the voices of those who know Joe Keller.

"It's just an awful situation not knowing if your loved one is in heaven or in a terrible situation on earth or out in the wilderness," Zoe Keller told Dateline NBC about her missing son. "Tomorrow will be a month and there is just nothing."

The teen disappeared on July 23rd while out running in a rural, mountainous area of Colorado.

Joe, who turned 19 the day after he vanished, had traveled from his home in Cleveland, Tennessee to a ranch near Antonito, Colorado with two of his childhood pals.

Keller, an avid runner and swim coach, and his friend Collin Gwaltney, whom he’s been close with since kindergarten, took off for a jog about 4:30 that afternoon. The group had arrived in Colorado that morning as part of their cross-county summer adventure.

Joe Keller (left) with friend Collin Gwaltney (right) on a trip they took last year to backpack the Appalachian Trail.

After about a quarter mile, the two split to run on different paths. They were to meet back at the ranch for dinner, said Gwaltney.

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"I took one road up and he didn't follow, which is normal because we run at different paces," Gwaltney told Dateline NBC. "But after two hours passed and he didn't come home, we went out looking."

No one has seen or heard from Keller since.

Thus far, there have been no real clues as to what may have happened. Volunteers poured into the remote Colorado area as searchers took to four-wheelers and horseback to scour the many trails breaking the landscape. The Keller family, along with five other close family members and friends, flew out from Tennessee the day after Joe vanished.

"Anything is possible at this point," Neal Keller told Dateline NBC. He remains in Colorado searching for his son. "There has been no sign, no clue, no nothing."

The official search by the Conejos County Sheriff’s office was suspended on August 4th. The handling of the case has perplexed many, as it’s been reported that Conejos officials initially refused offers for a search team from Bradley to join the efforts.

Two deputies from the Bradley County Sheriff’s Office, in Tennessee where the Kellers live, eventually were permitted to travel to Colorado just last week to try to uncover whatever leads they could. Officials say the FBI has also become involved, and foul play has not been ruled out. And like many others, they too have had to retire their efforts and head home.

No matter the circumstances surrounding the search, many across the country are doing everything they can.

"We're very grateful for all the volunteers," said Joe's mother Zoe. "Many who don't even know Joe have been looking or helping in some way and we cannot thank them enough."

Those close to Keller and his family have even looked into channeling the supernatural. A posting on the very active ‘Find Joe Keller’ Facebook page states that a person who is “new to discovering psychic intuitions’ shared a feeling that Keller is in western Arizona. Although some call it a long shot, fliers have been emailed to the Sedona Police Department and local news organizations, just in case.

"The community back here in Tennessee has been very supportive," said Gwaltney, who has since had to travel back home to begin his college classes. "There have been a lot prayer vigils and fundraisers. Everyone wants him home."

If anything is evident from the online community, it is that Joe is very much loved. The teen volunteered most Saturdays at the Salvation Army and was already registered for his second year of college, according to his father Neil. His parents say he was thinking of becoming a math teacher.

"It's not just been hard on our family; it's extremely difficult for his friends' families too. We’re all very close," Zoe told Dateline NBC. "This is something that really tests your faith. We’re just praying and hoping for others’ prayers as well.”

Keller disappeared in a mountainous area in Conejos County, Colorado. Conejos County Sheriff's Office

But one thing Joe's father believes they need to find his son is more resources. "The sheriff's department out here has limited resources and have done what they can, but we really need more help," Neal told Dateline NBC. "Someone who was out here on vacation camping may have seen something the afternoon of July 23rd and don't realize it. Attention may help identify those people who may live across the country. We just need help."

Joe Keller is described as 5’7” tall, weighing 160 lbs. with blond hair and hazel eyes. He was last seen wearing red running shorts with reflective strips on the sides and blue running shoes. He also has a slight British accent.

There is currently a $50,000 reward being offered by the family for information that helps bring Joe safely home. If you have any information, please contact the Conejos County Sheriff’s Office at (719) 376-6778 or the Bradley County Sheriff’s Office at (423) 728-7300.