On Thursday, the day Marine Cpl. David L. Reagan was fatally wounded in Beirut, his 18-year-old wife in Chesapeake, Va., received a letter in which he joked: "You know, if you see me on the news, it's probably because I've died, or got killed or something."

"He talked about it all the time," Rhonda Reagan said in a television interview yesterday. "He'd joke around about it and everything . . . . He was joking around. And it had to happen."

Reagan, 21, was the first American to die in Lebanon since 1,200 Marines landed in the country Wednesday as part of a multinational peace-keeping force. He was fatally wounded when a 155-mm. artillery shell exploded. He and three other Marines, members of a combat engineering platoon, were trying to defuse the shell, which Navy officials called an "ammunition bomb," on the tarmac at the southern end of the city's international airport.

After the explosion, Reagan was flown to the nearby amphibious assault ship Guam, where he died on an operating table.

Yesterday, residents of Chesapeake, south of Norfolk where the Guam was based, mourned Reagan's death.

"This is a tight little community, and when something like this happens the whole community goes a little bonkers," said Harold Dodge, principal of the Oscar Smith High School, from which Reagan graduated in 1979.

Dodge described Reagan as "a little, short guy, friendly as heck." A student with school spirit who never missed a ball game, he was an Air Force Junior ROTC cadet and won awards for "strong, sound" leadership, Dodge said.

Reagan, one of 16 brothers and sisters whose father is dead, was on work-study programs in high school, Dodge said. He had lived with his mother in an area known locally as "block city," a seven block area of one-story, concrete row houses, Dodge said. Reagan was one of three brothers who joined the Marines.

Dodge said Reagan once saw a man drop a $100 bill and spent several days trying to locate him. He did, and returned the $100. "He could have used that money, believe me," Dodge said.

Dodge said that Reagan, a B student, "did everything he could with what he had academically. He gave 110 percent of his God-given abilities."

Reagan considered the 1,000-student high school his "second home," Dodge said. "Whenever he would come home on leave, he'd come to school to say hello, and before he left, he'd say goodbye. I remember when he bought this used Mustang, an old fastback. He drove over just to show it off to me. He was so proud of it."

Following high school graduation, Reagan enlisted in the Marines and went to boot camp at Parris Island, S.C. He was assigned to the 2nd Marine Division at Camp Lejeune, N.C.

Reagan's mother-in-law told the Associated Press yesterday that when family members heard news that a Marine had died in Lebanon, they feared it might be Reagan.

"It was like intuition or something. Something told me it was David when I got through reading his letter and it flashed on the news at that point," said June Hunter.

"But why did it have to be David?" Reagan's sister, Shirley Dudley, asked. " . . . He had good training with the Marines and was making the Marines his career . . . . I guess you can say he never reached his career because he gave his life for his country."

Family members said, however, that they did not oppose the American presence in Beirut, said Dodge, who had visited the family yesterday.

"They feel like he was doing his job. They know that he loved the Marine Corps. The family doesn't want people to make his death political," Dodge said. "But they're pretty broken up, especially his wife. Right now, David's body is over there and Rhonda, she's just a kid. She's in shock."