With storms bearing down Monday evening, F. Patrick Marlatt hustled his daughters out the doors at the Maryland Fire and Rescue Institute on the University of Maryland, College Park campus, urging them to leave before the torrential rains and ferocious winds hit.

Within minutes, Marlatt would be buried under the rubble of the trailers that housed the institute, and his daughters, both students at College Park, would be dead, victims of a swirling wind that grabbed their car as they drove away.

Even before the College Park fire chief came to Washington Hospital Center to tell him the news, "I knew," Marlatt, his face scarred, said yesterday.

The tornado that raced through Prince George's and Howard counties just before dinnertime Monday, blowing roofs off buildings and felling trees with winds that gusted to more than 200 mph, destroyed two promising lives - one dedicated to safeguarding nature, the other to helping others, family and friends said yesterday.

Colleen and Erin Marlatt were more than sisters, they were best friends, they said. As the older sister, 23-year-old Colleen looked out for her baby sister. As the younger sister, Erin, 20, looked up to Colleen.

"My son, Michael, said, 'Thank God they died together.' Because Colleen would have never left Erin," Patricia Marlatt, their mother, her face tear-stained, said yesterday at the family's home in Clarksville. "It's a blessing that the two of them are together."

Yesterday, in the living room of the family's two-story gray house on Triadelphia Mill Road, with a steady stream of sobbing friends walking through, Patricia Marlatt spoke of her daughters and of the series of tragedies the family has endured in the past two years - from her colon cancer to her brother's fatal heart attack last fall to Erin's brain surgery in January.

After a semester off to recover, Erin, a sophomore sociology major, had returned to College Park and had filled her schedule with fun classes, her mother said. She had just left a theater class where she was building props for campus productions when she popped in on her father Monday. Her shoes were specked with paint as she waited for F. Patrick Marlatt, the assistant director of the fire institute, to finish work so they could go home.

Instead, Colleen offered her a ride. Normally, Colleen, a senior environmental science and communications major due to graduate in December, would have left campus earlier - her classes ended before Erin's - but she stayed Monday to do computer work for a communications class.

Colleen would always tell folks where she was and where she was going - using her cell phone to connect her with the world, her mother said. At 2:30 p.m., she spoke with her boyfriend, Ben Morse, at work at the Food and Drug Administration in Rockville, and told him she'd be staying late at school and would call him later. She called her mother about 4 p.m. to tell her she'd be bringing Erin home.

So when the storm hit and there was silence - when Colleen didn't answer her cell phone and the "I'm OK" call to Patricia Marlatt never came, they knew.

"I was hoping she was stuck in traffic, her cell phone wouldn't work," said Morse, 23, a criminal justice major who dated Colleen for more than four years.

University of Maryland President C. D. Mote said the women's car, a 1992 tan Mercury Sable, was apparently lifted over one of the campus dormitories before landing in a tree in a parking lot.

The same tornado that battered his daughters' car also destroyed the triple-wide trailer that housed the fire institute's training program, burying Patrick Marlatt, 51, with his legs trapped for about 45 minutes. He escaped, he said, with bruises and a gash above his right eye and was released from Washington Hospital Center on Monday night. All seven people in the trailer survived the storm.

The institute's staff knew Colleen Marlatt well because the young woman had worked there part time for two years.

"She was a wonderful, reliable girl - just the best student worker you could ask for," said Ann Davidson, director of administration at the institute.

At the Fifth District Volunteer Fire Department in Clarksville, where Patrick Marlatt was chief, the sisters were "family by association."

The suddenness of their deaths is difficult for people to comprehend, Deputy Chief Dave Moynihan said.

"I don't think the average person can readily identify with the sense of the loss," he said. "It's just not a tragedy you can adequately prepare yourself for."

The women were part of a large, close-knit extended family, raised with their brother, Michael, 26, first in Catonsville, then in Clarksville. Colleen and Erin went to St. Louis School in Clarksville through eighth grade, then to Notre Dame Preparatory School in Towson. Colleen graduated in 1996, Erin in 1999.

Both had lived away from home for part of their time in college. Colleen had moved home after the previous semester to save money. Erin stayed home after her surgery.

"What a blessing that was," said Patricia Marlatt, 50, an English teacher at Mount de Sales Academy. "It was nice to have them back."

The women's bedrooms reflect their personalities - Colleen, the organized sister, Erin, the eclectic one.

On Colleen's bed is a patchwork red-and-white quilt; on her shelves, books about the environment and Spanish. On Erin's walls are sheets of fabric in colorful patterns and a poster of Bob Dylan.

Both were musical, known for singing show tunes and Simon and Garfunkel tunes in the car. Both played the piano; Colleen played the harp that still sits in the family's living room.

When Erin was recovering from surgery - doctors at Johns Hopkins hospital removed a benign brain tumor in January after Erin complained of headaches - Colleen was always by her side, even spending nights in the hospital, Morse said. When Erin was at home recovering, Colleen would pick up flowers or games for her sister, he said.

The surgery, which resulted in a loss of about 15 percent of her hearing, affected Erin's outlook on life, making her more sensitive, her mother said.

Erin talked about those changes to Michelle Smelgus when the two worked weekends together at Zebop, a women's clothing store on Main Street in Ellicott City.

"She was just excited about being alive," Smelgus said.