On the way to show his grandmother the spot where he had recently tried ice fishing for the first time, Harland Dietrich's car broke through thin ice and sank beneath the frigid waters, the second fatal plunge of a car into Lake Minnetonka this year.

Dietrich, 31, and Mary Ann Haram, 87, were trapped underwater for about an hour Saturday afternoon before being taken to Hennepin County Medical Center, where they died at 7 p.m. Saturday, the Hennepin County Sheriff's Office reported on Sunday afternoon.

Relatives and friends speculated Sunday that Dietrich wasn't aware of the perils of the lake's unique channels when his car broke through thin ice in the channel connecting Gray's Bay and Wayzata Bay. The channel flows below the Hwy. 101 bridge.

Authorities said Dietrich and Haram were unconscious and not breathing Saturday when pulled from their submerged red 2006 Pontiac Grand Prix a little less than an hour after dispatchers received a 911 call from Dietrich's cellphone. Dietrich said "they were going down" and then the phone went dead, Hennepin County Sheriff Rich Stanek said Sunday.

Stanek said the total rescue time was typical if not better than average. The first responders were at the scene within five minutes of the 911 call and had to assess the incident from a safe area before making a call to the dive team. Most of the divers then had to drive to a storage area in Brooklyn Park to gather their equipment, head to the scene and don the cumbersome protective suits in frigid weather, he said.

Two weeks ago, 8-month-old Tabitha Markle died when her family's SUV plunged into a similar channel between Priest and Halstead bays. Tabitha's mother, father and 2-year-old sister survived, but the baby, who had been underwater for more than 15 minutes when divers reached her, died at a hospital three days later.

Authorities said alcohol may have played a role. The case was presented to the county attorney's office last week to review for possible charges.

Lake Minnetonka is known for such channels, where water moves and the ice is thinner. All but one of the 15 vehicles that have gone into the lake this winter -- including a snowmobile on Sunday afternoon -- have broken through in channels or where pressure ridges have weakened the ice, according to the Sheriff's Office.

Despite the latest deaths, Stanek said Sunday he doesn't plan to restrict access to one of the Midwest's most popular recreational attractions. Last February, the county banned cars, trucks and SUVs from all of its lakes and bodies of water after several vehicles went under because of unusually warm weather.

"We are just not seeing this happen on other county lakes," he said. "Last year was an extraordinary situation. I wouldn't hesitate to ban vehicles again if circumstances warranted it."

A special relationship

Dietrich and Haram lived together in Maple Grove, and they had a special relationship for years, said Andrea Dietrich, Harland's mother.

He had lived most of his life in Minneapolis, usually working two jobs since he was a teenager, she said. He was into sports and had planned a Super Bowl party at a local restaurant where he had worked in Maple Grove.

Kelly Schroeder, who met Dietrich years ago when she managed a Denny's restaurant in Brooklyn Park, called him her "adopted son." His most recent jobs were working for Crave when it opened in downtown Minneapolis and a new restaurant in Robbinsdale.

"He was very popular wherever he worked and he had lots of friends," said Schroeder. "He was a big teddy bear."

Every weekend, she said, Dietrich took his grandmother out for a drive and a bite to eat. Last week he had gone ice fishing for the first time with a friend and had been fascinated by the experience.

"He talked all week about ice fishing," said Schroeder. "And his grandmother loved seeing different things."

Dangerous ice

On Sunday, a lonely bouquet of yellow and purple flowers lay on the snow-capped ice near the frozen-over hole and "Thin Ice" signs by Gray's Bay Bridge. A few snowmobilers stopped nearby, then took off down the bay. Katie Clark and her dog Smoky walked over on the lake from their nearby Wayzata home to say a prayer for the two who perished, she said.

"If you snowmobile on the lake you have to know the rules," Clark said. "The rules are you stay away from the channels, whether on foot, snowmobile or a car. People don't understand you got running water [through the channels] and they never quite freeze."

Earlier Sunday afternoon, on the other side of the lake, Rick Reinert of Mound was drilling 20-inch deep ice fishing holes in Black Lake about 1:15 p.m. Sunday when he saw a snowmobiler approach the Black Lake Bridge channel. He said the guy was heading toward the road and then changed his mind and turned toward the bridge. The guy hit the gas, popped the sled up and spun into the channel.

"When he hit it, he went down like a rock," Reinert said. "He popped right out, but his sled is on the bottom."

The only three ice-related fatalities in Minnesota this winter season have been on Lake Minnetonka, although before 2013 the last fatality on Minnetonka was in 2007, when a 56-year-old fell through the ice on a snowmobile. Since the 2006-2007 winter season, 25 people have died on state lakes. One possible factor for the deaths and crashes this year could be a lack of snow. People have been able to drive freely around the lake. If there were more snow, drivers would follow a plowed and safe road.

On Minnetonka, the ice where Saturday's incident occurred may have appeared thicker because of recent cold weather. But because of the frequent fluctuations between cold and mild weather this season, the ice isn't safe, Stanek said.

He noted that large, electronic billboards with caution messages have been placed around the lake. Dozens of deputies and officers patrol the lake daily, and Stanek and other law enforcement officials are using the media to educate the public on the lake's dangers, he said.

The sheriff also noted the "Thin Ice" signs placed in front of Minnetonka's channels, saying people would have to drive around them.

"I don't know why somebody would take such a risk," Stanek said Sunday.

Staff writer Jim Adams contributed to this report. David Chanen • 612-673-4465