On Thursday morning, the brother of the missing mom launched a massive search for his sister, who vanished in the mountainous hills of Colorado on Mother's Day
Suzanne Morphew
Suzanne Morphew
| Credit: Chaffee County Sheriff's Office

The older brother of missing Colorado mom Suzanne Morphew launched an independent search on Thursday for the remains of his younger sister, who he believes was the victim of foul play.

"My sister was murdered," her brother, Andrew Moorman said, ABC affiliate Denver 7 reports. "And she was hidden within a three-and-a-half-hour window. So that — I can draw a circle on that and tell you she's within that circle. And that's what I know happened."

Morphew, 49, went missing on Mother’s Day on May 10 after she is believed to have gone on a bike ride in Maysville, where she lives with her husband, Barry Morphew, and her two daughters.

Suzanne Morphew
Suzanne Morphew
| Credit: Chaffee County Sheriff's Office

The Chaffee County Sheriff’s Office, the Colorado Bureau of Investigation, and the FBI conducted 10 searches for her, to no avail.

Moorman’s independent search, which the Chaffee County Sheriff’s Office and the CBI are supporting, will run from Thursday through Tuesday.

“I just want to find my little sister,” Moorman told FOX21 News. “I want to bring her back home and give her a proper burial.”

Hundreds of volunteers from Colorado and other states, including Indiana, where Moorman and Morphew grew up, are helping him.

A Gofundme to help defray the costs associated with the search has raised nearly $13,000 as of Thursday morning.

Volunteers will walk the rough, mountainous, wooded terrain in the area to look for any sign of the missing mother.

They will scour nearby lakes with boats and SONAR equipment and use search dogs and drones to find any clue as to what happened to her.

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Moorman told Denver 7 that he will be searching in four specific areas using satellite images to guide him.

“I have very good intelligence,” he told Denver 7. “Very good intelligence. Maybe I don't know everything the FBI knows, but I know a bunch of it."

He added, "I'm going to get results.”

The last time Moorman saw his sister was at Christmas, he told the station. On April 30, he wished her a Happy Birthday.

“She responded back to me on May the 2nd,” he said. “And that was the last communication I had with her.”

On the day Morphew went missing, Barry was out of town for work. Her two daughters were on a camping trip in another state.

The well-liked, athletic mom’s friends called one of her neighbors when they couldn’t reach her, and the neighbor called police to report her missing.

Investigators searched the area and found her bike at the bottom of a hill and one personal item – but couldn't find her.

Her husband has said he believes she may have been attacked by a mountain lion.

suzanne morphew with her husband barry
Barry and Suzanne Morphew

Moorman thinks otherwise, saying that had had been attacked by a mountain lion, there would be some evidence of that, Denver 7 reports.

He doesn’t think she left the bike where it was found, either.

"You couldn't have ridden off that cliff without being severely hurt," he said, Denver 7 reports. "There certainly would have been evidence of injury at the bottom of that hill and there was none. So I believe the bike was picked up and thrown over the hill by human hands."

Barry and Suzanne's daughters haven’t commented publicly on the search.

Suzanne Morphew
Barry Morphew
| Credit: Find Suzanne Morphew/Facebook

Morphew’s husband posted a reward of $100,000 for information about her disappearance, which a family friend increased to $200,000.

Anyone interested in signing up for the search can visit this site.

This remains an open investigation. The sheriff’s office is asking anyone with information to call a tip line at 719.312.7530.