With pacifist parents and no family members in the military, Karl Linn was an unlikely Marine.

But the events of 9/11 changed him.

"I think he wanted payback, as well as some discipline," Richard Linn said of his oldest son. "I'm the Peace Corps type, but I didn't object."

So after he graduated from James River High School in 2002, Karl Linn earned the blessings of his family and joined the Marines. Lance Cpl. Linn and his unit -- the 2nd Platoon, Company C, 4th Engineering Battalion out of Lynchburg -- shipped out to Iraq in the fall.

Now, the unthinkable has happened.

Linn and three others from his unit were killed Wednesday in Iraq's Anbar province during an ambush on their convoy. Linn, 20, was from Midlothian. The other victims were identified as Sgt. Jesse Strong, 24, of Orleans, Vt., a student at Liberty University in Lynchburg; Cpl. Jonathan Bowling, 23, of Stuart; and Cpl. Christopher Weaver, 24, of Fredericksburg.

Linn's interest in engineering was evident from an early age. In 1998, he and five classmates from St. Michael's Episcopal School in Bon Air designed a winning entry in the Junior Solar Sprint -- a miniature solar-powered car. Later, Linn founded James River's robotics team.

"He was not so much of a tinkerer as an observer," Richard Linn said. "He was a very quiet person, very smart, very off-the-wall. They used to call him 'Crazy Karl' in high school because they never knew what he would do next."

After James River, Linn joined the Marine Corps Reserve but chose a delayed-entry program so he could start college. He enrolled in the mechanical-engineering program at Virginia Commonwealth University and participated in "weekend warrior" basic training while attending classes, specializing in combat engineering. Then, last year, Linn's unit was activated. They were sent into combat in November.

Between missions, Linn was keeping himself busy e-mailing his family, playing with his Canon PowerShot A60 digital camera and updating his new Web site, karl.linn.net. He posted photos of himself, grinning widely, posing with his machine gun and Humvee.

"Other than being tired recently because of 12-hour days patrolling, he'd say the food was lousy and it was chilly," Richard Linn said yesterday. "He was more concerned about when we were sending him more socks and gummy bears, which were apparently in short supply."

Even though he was able to call home only once, at Christmas, his family could see his adventures online. They knew he was safe.

On Wednesday morning, Richard Linn was 40 miles north of Richmond on a business trip when he got a call from his mother. The Marines wanted to talk to him at home.

"You're never prepared. My wife just didn't even want to think about it. She was always scared, from the time he was in boot camp, but she hoped and prayed and tried not to dwell on it. I knew this could happen. I felt the odds were good that it wouldn't, but I've never been a gambling man"

Linn is survived by his father and mother, Malisa, and brother, Tan, who is 15 and a sophomore at James River.

Rest in peace, Cpl. Linn.