-- Matthew and Mark Weaver made it look easy -- the way they made friends, excelled in school and piled up sports and extracurricular activities, always with winsome smiles. But those who knew them knew better.

"They worked hard for what they got," said Rob Maegerle, one of the boys' former swim coaches. "I hate to say they had the world in their hands, but they did. They had incredible futures in front of them."

Those futures came to an inexplicable end Thursday when the boys and their parents were found dead in their home in a town near Wilmington, Del. Police say the father, Davis Weaver, shot his sons and his wife, Nancy, as they slept, then turned the gun on himself.

The apparent murder-suicide has left friends and acquaintances clueless as to what psychological catastrophe could have led to the tragedy. They say they saw no signs of a crisis. Pennsylvania State Police provided no new details Saturday.

Matthew, 21, was a student at the University of Maryland. Mark, 18, was about to enter the U.S. Naval Academy with ambitions of becoming an astronaut.

He was to graduate today from St. Mark's High School outside Wilmington, from which his older brother had graduated in 2003. Both were honor students and competed in several sports, including swimming and track. Mark was voted class vice president three years running.

Their deaths shook the 1,500-student Catholic school. A half-dozen school officials gathered to consider how to proceed with the commencement ceremony. "We want the kids to remember Mark and Matt, but we also want it to be a day of joy, and that's going to be tough," said Assistant Principal Timothy Neal.

Chelsea Brown, 18, who served on the student council with Mark, remembers meeting him in a history class when they were freshmen. Even then he was talking about the Naval Academy and his goal of becoming an astronaut.

"He said the Navy had cooler uniforms than anyone else, especially the white formal ones," Brown said.

The boys' parents were longtime educators who had worked for years in the Christina School District in Delaware: Nancy Weaver, 51, as a teacher at the Margaret S. Sterck School-Delaware School for the Deaf, and Davis Weaver, 61, most recently as a guidance counselor at F.D. Stubbs Intermediate School in Wilmington. He had been on medical leave since March and had plans to retire at the end of June. School district officials have not disclosed why he was on leave.

Both were actively involved in their sons' lives, friends recalled. They attended swim and track meets, volunteered for prom duty and took family trips.

On Wednesday night, the whole family attended the St. Mark's baccalaureate service for the graduating class. The next day, Mark failed to show up for graduation rehearsal -- the first clue of the tragedy, but one that nobody caught on to.

"We just thought if Mark missed this, it had to be for a really good reason, because he was never late for anything," Brown said.

In his two years at the University of Maryland, Matthew had built expansive circles of friends in the agriculture program, where he studied, and at the pool, where he worked as a lifeguard and swam for the university's club team.

Helen Garst, 19, lived in Denton Hall with Matthew during their freshman year and decided to study with him because he was such an intense student. Matthew had charged into one of the more difficult majors, landscape architecture, and quickly excelled, she said.

"He was always in the studio," Garst said. "You have to do the drawings and the layouts, but he didn't seem bothered by it."

As hard as he worked, she said, he never came across as bookish. The two both served as "Ag Ambassadors" to help recruit students.

Abbie Thompson, 22, who worked as a lifeguard with Matthew, said he was the guy the others turned to whenever they were in a jam. He was quick to volunteer when the team needed someone to swim a relay leg or when someone had to miss a lifeguard shift.

Jessica Suagee said she and Matthew did a presentation for potential donors to the university's agriculture program this spring. His presentation was of an urban garden he had designed.

"He told them that the point of the garden was to reduce depression," Suagee recalled. "A place every adult could go and forget all the daily pressures of life."

Mosk reported from Washington.

The Weavers were shot dead in an apparent murder-suicide in the family's Pennsylvania home Thursday, police said. Friends said they had no idea that anything was amiss.