Out of the corner of her eye, Kate Coakley saw them coming through her front gate.

Two U.S. Marines in full-dress uniform. White gloves. Hats. Shoes polished to a high gloss. And a chaplain in tow.

None of them had ever visited Coakley's home in Jupiter, Fla., before. But there was no uncertainty in the way they maneuvered. They knew instinctively where they were headed. And why.

"I came home from the gym, and I hadn't been here long. Not long at all," Coakley said Wednesday. "And I see these Marines in full-dress uniform and a chaplain coming through my gate.

"And I knew. I just knew they were coming for me, to tell me," Coakley said. "You know. You know these things."

Her son, Roger "R.J." Muchnick, was dead. He was one of seven Marines killed during a training exercise at the Hawthorne Army Depot in Nevada on Monday when a 60 mm mortar shell exploded in its launch tube.

Muchnick, 23, served tours of duty in Afghanistan and Kuwait. He was the eldest of four children raised by Coakley and her ex-husband, also named Roger. R.J. was the first to leave the family's nest after graduating in 2008 from Staples High School in Westport.

Along with his parents, Muchnick is survived by his brother, Will; twin sisters, Grace and Avery; and his paternal grandfather, Jerome Muchnick.

All his life, Muchnick heard stories about the military service of his uncles and great uncles. It was a matter-of-fact part of his family's history, like having blue eyes or being competitive.

On his Facebook page, R.J. Muchnick has several hundred friends listed. And he knew every single one of them, his mother said.

"R.J. was one of the most social people you ever met. He has friends who he's known since he was 2 years old. He has friends from preschool and all the way up through Staples and beyond," Coakley said. "He's never lost a friend. Not his whole life."

While at Staples, Muchnick was a linebacker and running back on the school's football team and also played lacrosse. In a 2008 profile of Muchnick in the Westport News, he talked about the benefits he found in playing both sports: "Playing football and lacrosse year-round makes you into a better athlete."

On the lacrosse and football fields, Muchnick forged close friendships with a number of teammates. In interviews Wednesday, several remembered him as a highly competitive and driven player, and a charismatic and ebullient presence off the field.

"Everyone always liked Roger and gravitated toward him -- he was never at a loss for a joke," recalled Jason Zins, a friend and lacrosse teammate since Muchnick enrolled at Coleytown Middle School in Westport. "But he also really hated to lose. He really pushed everyone around him to be their best. And he always had the best shot on the team."

Dylan Bobrow, who played lacrosse and football with Muchnick from seventh grade until they graduated from Staples five years ago, said Muchnick was an exemplar of commitment and national service when he decided to become a Marine.

"He was very passionate about the Marines and his country," Bobrow said. "He was in good spirits and he was excited about his training. Unfortunately, he died doing it, but at least he died doing what he loved."

Staples Principal John Dodig on Wednesday recalled Muchnick as an outgoing and popular student.

"He was the kind of kid, who, if he ever decided to become a salesman, there'd be no stopping him," Dodig said. "He had an electric personality."

After graduating from Staples, Muchnick enrolled at Eastern Connecticut State University in Willimantic, where his biography on the university's website said he was a four-year member of the lacrosse and football teams.

"He is, he was, a very bright young man," said R.J.'s grandfather, Jerome Muchnick, from his Philadelphia home, where friends and neighbors gathered Wednesday to mourn his grandson. "He goofed off a little bit, and his father says to him, `If you're not serious about this, you better find something else to do with yourself.' "

So R.J. Muchnick, the young man with the military DNA, enlisted in the Marines. He was stationed with the 2nd Marine Expeditionary Force at Camp Lejeune in North Carolina.

Whenever Jerome Muchnick and his grandson spoke, he recalled, "R.J. wouldn't hang up the phone without saying `I love you, grandpa.' And he was always texting me, things like that, too."

Originally from Weston, R.J. Muchnick moved to Westport when he was in middle school, attending seventh and eighth grades at Coleytown Middle School. He then briefly attended Fairfield College Preparatory School before transferring to Staples High during his sophomore year.

Muchnick was a versatile athlete from his childhood. He was a Little League pitcher until fifth grade, and began playing football when he was in third grade. He also played basketball from kindergarten to sixth grade.

"He was a competitive person," said Mary Joyce Colwell, a longtime family friend. "He was personable and he looked out for others. He had a lot of compassion, and when all of our kids were growing up in Westport, he always looked after the younger ones. He made sure that whatever was going on, they didn't get left out."

The structure and the team-building aspects of the Marines, Colwell said, are facets of the military that dovetailed well with Muchnick's personality.

"I've known him from the time he was 2 years old. He was a leader even as a kid. He was very determined, and he showed empathy toward others," Colwell said. "Being the eldest of four kids, he was a wonderful big brother, always looking out for people."

Even with his warmth, R.J. didn't always give others an easy time, even if they were younger and they were playing a sport.

"They'd all get out and play lacrosse and he showed no mercy on the field," Colwell said. "He didn't throw games. If they beat him, they did so fair and square."

Westport First Selectman Gordon Joseloff, in a statement issued Wednesday, said the Marine's death was a sad day for the town.

At Staples, Joseloff said, Muchnick "was well known as a popular football and lacrosse player, and was well liked by his friends, teachers and coaches.

"He is the second Staples graduate on active duty with the Marines to die in an accident in little more than three years, and our community once again is in shock," the first selectman said. "Our hearts go out to the Muchnick family and friends. We deeply share their loss."

In a strange way, R.J.'s mother, Kate Coakley, said that she considers herself fortunate.

She recalled how her grandmother, Jeanette Coakley, agonized for years when she got a similar visit during the Vietnam War. The military arrived on her doorstep to announce that her son, Navy Lt. Commander William Francis Coakley -- a jet pilot and Kate Coakley's uncle -- had been shot down over Hanoi on Sept. 13, 1966.

No one knew if he had survived the crash or had been taken as a prisoner of war by the North Vietnamese. It took until May 1989 for William Francis Coakley's remains to be identified and returned to his family for burial.

"I went to that funeral for my uncle and R.J. went with me," Kate Coakley said. "I was pregnant with him."

The Associated Press contributed to this report.