A father and his three children were killed when their kayak capsized on Lake Superior on Thursday, officials said. Their mother was the sole survivor of the kayak accident.

A father and his three children were killed when their kayak capsized on Lake Superior on Thursday, officials said. Their mother was the sole survivor of the kayak accident.

The family from Loyal, Wisconsin, set out from Madeline Island in an open-top tandem kayak Thursday for a 4-mile paddle across open water to Michigan Island. But their 13½-foot kayak capsized after the wind picked up.

Eric Fryman, 39, and his three children, Kyra, 9, Annaliese, 5, and Jansen, 3, were found dead in the frigid water. Only his wife, the children's mother, Cari Mews, 29, survived. All of them wore life jackets. Coast Guard officials said hypothermia was probably a major factor in the deaths, especially of the children.

"Even with all the required safety equipment and all the right training, anything can happen when you get out on the lake," said Coast Guard spokesperson Justin Sickler told CBS Minnesota.

Cari Mews' sister, Bobbi Jo Mews, told CBS Minnesota the family was on their last "before school starts" vacation, visiting Madeline Island on Lake Superior.

"They loved to go camping together and they took their kids everywhere and explored the world," said Mews.

Mews said that when she saw two short, frantic text messages from her sister Thursday night, she immediately knew something was wrong.

"I got a text message that said '911,' and then immediately following, 'Michigan Island.' I knew that they were going kayaking that day … I just knew I had to call the police to see if they could go look for them," said Mews.

Bob Krumenaker, superintendent of the Apostle Islands National Lakeshore, told the Star Tribune of Minneapolis for a story published Sunday that it was a sobering reminder of the vastness and danger of the largest of the Great Lakes.

Krumenaker, whose staff assisted with the rescue efforts, said the Apostle Islands are mostly undeveloped and forested, with rocky shorelines and long distances between each island.

"Some of the places that people want to go kayaking are incredibly attractive but also deceptively dangerous," he said. "This particular incident happened in a place that is not often traversed by people on kayaks, and for good reason."

Paddlers crossing open water between islands can become exposed to strong winds and waves, he said. Storms can also come up fast, he said, although the one that struck Thursday was predicted in advance.

Gail Green, director of Living Adventure, an outfitter near Bayfield, Wisconsin, that specializes in kayak tours of the Apostle Islands, said open-top kayaks like one the family used are good for calm, sunny days close to the shore, but can fill with water and capsize in rough conditions.

Krumenaker said lake-crossers should practice capsizing and recovering, something Green's company does with paddlers before overnight trips.