UPDATE: Authorities Confirm Cause of Death of Las Lomas Students

Authorities have confirmed that a rainy Saturday afternoon rafting trip in Walnut Creek turned deadly for two students whose bodies were found Sunday in the waterway that empties into Suisun Bay.

The bodies of Matthew Miller, 16, and Gavin Powell, 17, both Las Lomas juniors, were more than five miles north of where they told friends they planned to begin their rafting adventure Saturday.

"It's horrible," said Contra Costa Sheriff's Lt. Eric Navarro. "I have kids that age. I just feel horrible for the kids and for their families." 

Authorities also confirmed Monday that the two boys both died of asphyxia due to drowning. Contra Costa Sheriff's spokesman Jimmy Lee said autopsies on the two were completed Monday. 

The waterway known as the Walnut Creek Canal meanders north through downtown Walnut Creek, past Bancroft Road and through central Contra Costa County, eventually winding past the Sun Valley and Willows shopping centers as well as Buchanan Field airport before emptying into Suisun Bay. 

During and following a heavy winter storm, the rain-swollen waters of the creeks and flood control channels in Walnut Creek move fast and cold. The water becomes filled with debris, is below 50 degrees and more than ten feet deep in parts, Navarro said. 

Friends told the boys' parents, and later told authorities, that the two friends planned to start their journey somewhere near at about 2 p.m. Murwood is just off Rudgear Road. The boys were in a two-person inflatable raft. 

They told a friend to meet them at a location at 4 p.m., Navarro said.

When Matthew and Gavin didn't show up, the friend assumed they had found another ride and was not concerned enough to tell anyone. Navarro said investigators are trying to determine where the teens had planned to rendezvous with their friend. 

None of the boys' parents knew about the rafting trip, according to authorities. Gavin's parents grew concerned when their son failed to respond to a call to his cell phone Saturday evening. They began checking with friends and learned about the rafting trip.

Matthew's parents, likewise, found out about the rafting trip Saturday evening, said Walnut Creek police Lt. Bryan Hill. 

After midnight, each of the families reported their son missing. Powell's family reported it to the Sheriff's Department because they live in an unincorporated area of Walnut Creek.  

First thing Sunday morning, Walnut Creek police and Contra Costa sheriff's crews began searching for the boys with the help of the Contra Costa Consolidated Fire District and an East Bay Regional Parks district helicopter. The search swelled to about 85 volunteers, Navarro said.

At 8:30 a.m., searchers found the deflated raft where Walnut Creek flows by Bancroft Road and Bentley Street.

About 11:30 a.m., searchers found the body of Matthew Miller where the waterway passes near Imhoff Drive, just north of Buchanan Field airport and Highway 4. 

Two hours later, searchers found the body of Gavin Powell near Stanwell Drive and Concord Avenue. 

Neither boy was found wearing a life jacket but they were wearing helmets, said Contra Costa Sheriff's spokesman Jimmy Lee. 

The creek isn't easy to reach. Murwood Elementary School's cyclone fences stand between the school's playing field and the creek. High cyclone fences line the creek in many other spots in Walnut Creek. However, Hill said there may be spots where people, determined to get down to the water, can get in. If nothing else, they can scale the fences. 

A woman who works at Caspers Famous Hot Dogs said Walnut Creek police and Contra Costa Consolidated Fire trucks blocked off South Broadway about 11:45 a.m. Sunday and appeared to be conducting a search in the canal.

The water there looked deep and was moving fast after heavy rain and storms.

The spot along Walnut Creek Canal, where fire and police were searching for signs of Matthew and Gavin, is about a fifth of a mile from where a car carrying a family of three crashed into the canal in April.

That Sunday in April, there also had been a storm, with a heavy downpour in the late afternoon. Walnut Creek was swollen with rushing, cold water. 

The Hogan family, longtime residents of this community, was driving north on San Miguel Drive, toward Mount Diablo Boulevard. A medical condition caused the driver, 40-year-old Tim Hogan, to lose control of the Honda and crash through the fence and land in the canal. His mother and father, Janet and Jim, both in their 70s, climbed out of the car, but Jim was injured.

The water quickly carried the couple north. Janet Hogan, 75, was plucked from the water in a dramatic rescue, but her son was found dead in the Honda. Her husband, Jim Hogan, 79, was found dead several days later in the canal near Buchanan Airport in Concord, not far from where Matthew Miller and Gavin Powell were found.