Reuben Waithaka traveled 8,200 miles to watch his first grandson graduate from high school in Alabama. He arrived from Kenya six days early with sentimental gifts tucked in his suitcase, faded photos of his own son at a young age, and matching African print shirts for his son, grandson and himself.

But they never got a chance to stand together ? three generations of men ? proudly wearing colorful, coordinated outfits.

The morning after he and his wife, Elizabeth Barua, landed in the US, Waithaka walked out of his son?s house in Calera, Alabama, and vanished.

The home?s doorbell camera captured the 72-year-old stepping out onto the driveway at 11:08 a.m., dressed neatly in khakis, a checkered blue- and-white shirt and black shoes.

About half an hour later, surveillance footage recorded him walking into a gas station almost two miles way. He waved at the store attendant, headed into a rest room and left through the back door, never to be seen again.

?He just got here. And then he was gone,? says his grandson, Byron Arua, 17, who graduated five days later without his grandfather present.

Seven weeks later, there?s been no sign of Waithaka. Police have scoured wooded areas around Calera ? a city of about 19,000 people some 30 miles south of Birmingham ? using helicopters, drones, off-road vehicles, tracking dogs, and infrared heat-seeking cameras. So far, they have found nothing.

?Sometimes I regret why I asked my parents to come for my son?s graduation. I find myself wondering, ?What would I have done differently??? says Waithaka?s son, Willington Barua. ?Maybe if I hadn?t invited them, my dad would still be with us.?

The family has retraced Waithaka?s steps and watched the surveillance footage over and over, searching for clues. How does a 5-foot-5, 160-pound man disappear in broad daylight ? in a foreign country where he barely knows anyone?

They?ve considered the possibility that Waithaka had undiagnosed dementia or another condition that was triggered by the stress of being away from home. It?s not uncommon for people with dementia to wander away from home, especially when they?re in unfamiliar surroundings, experts say.

He must be so scared, says his daughter, Emily Barua, her voice trailing off as she draws a long breath.

?I want to be hopeful, I really do,? she says. ?But sometimes I wonder ? did he sit somewhere and fall asleep in the heat and never (wake) up??

The family has replayed the moments leading up to Waithaka?s disappearance and wondered: Did they miss signs that something was wrong?

He wasn?t himself on the flight to the US

Looking back, Waithaka seemed restless on his trip to the United States. At the time, his family figured it was just exhaustion from the 18- hour journey, his son says.

His parents? flight took off from the Kenyan capital of Nairobi on May 13. Waithaka drove his small sedan to the airport, where they boarded a Lufthansa flight through Frankfurt, Germany, to Atlanta.

Just before heading to the airport, he did his usual routine ?- picked up some yard litter, fed his five German Shepherds and cleaned up their space. He?d hired someone to care for the dogs while they were gone, his son says.

The flight to Frankfurt went fine, but things went downhill on the journey?s second leg to Atlanta. Waithaka became incoherent and agitated, and a flight attendant had to step in to help his wife keep him seated, his son says.

Waithaka?s unease didn?t end after landing in Atlanta. He appeared confused, and fell and hurt his knee when he tried to go the wrong way on an airport escalator, his son says. His limp from that fall is visible on the gas station security footage.

Barua took his father to the ER once they arrived in Calera. He was discharged in the early morning after a CT scan of his head and some bloodwork came back normal, Barua says.

Jetlagged and exhausted, Waithaka showered, took a nap and ate a breakfast of fried eggs and tea. Then he stepped outside. His wife followed initially, but when she rushed back to close the garage door, he was gone, his son says.

His family begged people to stop giving him rides

Waithaka got two rides from motorists after he left his son?s home that morning, giving him a significant head start. His family believes those rides changed everything.

Investigators interviewed both people who gave him rides, says Calera Police Chief David Hyche. Waithaka first asked a neighbor to drop him off eight houses away, mistakenly thinking it was his son?s home. There, he flagged down a DoorDash driver and asked for a ride ?to town.? The driver stopped at a gas station and Waithaka told him that location was fine, Hyche says.

His last confirmed sighting was at the gas station ? at 11:43 a.m.

A resident later reported seeing someone matching Waithaka?s description entering a hunting club near the gas station. The woman told police that he crawled under a gate and disappeared into a wooded area, Hyche says.

Police have interviewed the people who live in the area several times. Investigators speculate Waithaka may have caught another ride at a truck stop behind the gas station ? potentially out of town, Hyche says.

Shortly after he was reported missing, his family went on local television and begged people to stop giving him rides. They feared each ride was taking him farther from home ? and from them.

?It is still a possibility that he?s in that wooded area because it is just so large,? Hyche says. ?But we were searching with many resources as fast as possible because it?s a very hot and very thick area. And someone of his age, we needed to find him as fast as possible. So after several days of intensive ground searching, we moved ? to the hope that someone had given him a ride.?

After Waithaka went missing, many of the town?s police officers worked 18 straight days without a day off, Hyche says. The leads have tapered off, but he?s promised the family that detectives won?t stop search searching until he?s found.

In the days since Waithaka vanished, residents have distributed flyers and combed wooded trails. Hyche says offers for help poured in.

?We couldn?t even respond to them all,? he says. ?We had to turn away well-meaning citizens during the nighttime infrared searches and K-9 searches to avoid a false positive.?

Waithaka had his Kenyan phone with him when he disappeared. Hyche reached out to the FBI in Nairobi to ask the local carrier to help track it, a process that took several days.

It said the phone last pinged in Frankfurt, indicating it may be in airplane mode, making it difficult to track, Hyche says. The Kenyan did not have his passport, which contains his B-2 visitor?s visa to the US. He may have had some money in Kenyan currency but none in US dollars, his family says.

detectives have searched abandoned buildings in the area and are regularly reaching out to homeless shelters, hospitals and immigration officials to check whether Waithaka has appeared in their databases, Hyche says.

?It was urgent to really do all we could to try to find him,? he says. ?It?s just such a sad case, but it?s also given us an opportunity. I did not know we had Kenyans living here. Well, maybe because none of them have

ever been in any trouble.?

His relatives remain haunted by questions

Waithaka has four children: two in Kenya and two in the US, including daughter Emily Barua, who lives in Renton, Washington.

Willington Barua has mostly lived in the Birmingham area since he immigrated to the US about 25 years ago. He was drawn to Calera by its small-town charm and mild winters.

On May 20, five days after his grandfather vanished, Byron Barua graduated from Calera High School.

The family joined hands and had a moment of silence for their missing patriarch before the ceremony. As Byron, 17, crossed the stage to get his diploma, his relatives clapped and cheered, determined to stay strong for him.

?It was tragic, but I tried not to let it get to me or bring me down all the way,? Byron says of his missing grandfather. ?I pray for him to stay safe.?

As the days drag on without answers, fear takes over and the family is haunted by endless questions. Was he a victim of foul play? Is he alive? And if he is, how is he surviving with no money?

Willington Barua says his parents? flight arrived in the late afternoon, and he wonders whether his father was going through ?sundowning,? a late-in-the-day symptom which can affect people with Alzheimer?s disease and other types of dementia, according to the Mayo Clinic. It causes confusion, anxiety and aggression, which in turn leads to pacing or wandering.

Waithaka?s wife, Elizabeth Barua, returned to Kenya on June 20 to be with loved ones. She declined to be interviewed when CNN reached out to her and is too distraught to speak with the media, her son says.

The couple has been to the US twice before: in June 2017 and May 2019. On both previous trips, Waithaka?s health appeared fine and he had no issues, his son says. His parents even extended their 2019 visit by several months.

June 3 marked Waithaka?s 73rd birthday. His son had planned a party for him on Father?s Day ? his parents? last weekend in the US before they were scheduled to return to Kenya.

He was going to roast a goat ? a Kenyan delicacy ? and invite friends and family from all over the US to celebrate his dad. Maybe they would have worn their matching shirts.

But there was no party.

What happened to Waithaka remains a mystery. Barua owns a trucking company, and he tapes flyers at rest areas and truck stops wherever he goes. Every time he passes a wooded area, he slows down and peers into the trees.

And every time his phone rings, his heart races. He picks up with anticipation and fear, hoping the call will bring answers. The not knowing, he says, is the hardest part. (CNN, excluding headline)

? Reuben Waithaka had brought this old photo of him and his sons, including Willington Barua, right, to share with his grandson. Courtesy Emily Barua

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