Marine Staff Sgt. Alexander M. Ortega's last letter from Beirut was marked by disillusionment. He was, his family said, "a good Marine, a loyal Marine," but he saw little promise for the international peace-keeping mission that took him to the Middle East.

"Well, over here it is still the same," Ortega wrote earlier this month to his sister, Bonnie McKean, in Rochester, N.Y. "Last week we got bombed pretty good . . . . When the bombs hit, all you could see was Lebanese people flying and dying. We had a couple of Marines hurt, but nothing serious. The best part is we got to fire back for the first time. So I guess I'm a combat veteran now. Ha. Ha."

Ortega, 25, is now a casualty of combat. He was one of two U.S. Marines killed early yesterday by mortar fire, apparently aimed at nearby Lebanese army positions. Ortega and 2nd Lt. Donald George Losey, 28, became the first Americans in the multinational peace-keeping force in Lebanon to be killed by hostile fire.

Based on letters they wrote their families, the two Marines had differing feelings about their mission.

Ortega wrote with dismay of a war that seemed irrepressible and Lebanese who appeared always hostile. Losey wrote stoically of boredom, except when he was assigned patrol duty.

"He Ortega would always write that his mission was peace, but there was no peace," said Barbara Gillespie, Ortega's aunt. "He said the Lebanese people hated the Americans, but there was hope for the children. He thought he could make friends with the children. He asked us to send him candy, so he could give it to the children."

Candy was in the mail when news of Ortega's death reached his parents, Alexander and Helen Ortega of Henrietta, N.Y., his relatives said.

"He Losey was bored, except for the patrols," according to John Losey, one of the Marine's five siblings. "He liked to patrol because he could meet the people." Ortega and Losey went to Beirut in May. But Ortega went reluctantly, while Losey went out of his way to get the assignment.

Ortega, who enlisted in the Marines during his senior year of high school, had already put down roots. He and his wife, Robin, had just bought a mobile home in Jacksonville, N.C., where he hoped to spend several years as a recruiting officer. They had a 2-year-old daughter, Heather, and were expecting their second child in January. Ortega expected to come home in December.

"He was so excited he was going to be a dad again," said Ortega's sister, Bonnie. "He wrote about it in every letter."

Losey was single and "looking for his future," John Losey said. He "drove himself hard. He was interested in being the best. That's the thing he always tried for."

According to his brother, Losey spent four years in the Army after being graduated from high school in North Carolina, rising quickly and serving in the honor guard in the Berlin Brigade.

Losey was graduated last year from the University of North Carolina in Greensboro with a degree in anthropology.

"He liked anthropology because he was always interested in people, even more than in places," his brother said.

After college graduation, Losey joined the Marines as an officer and was stationed at Camp Lejeune, N.C. He had not yet settled on the military as a career, according to his family.

But he "pulled strings so he could go to Lebanon. I think he felt it was a duty," said John Losey, who added that his brother's letters mentioned no fears or dangers. "He said the people were fairly friendly for the most part."

Ortega saw the Marines as a career. He enlisted during his senior year in high school in Rochester, his relatives said, in part because the economy was so sluggish that there was no hope of factory work.

"He just felt it was a good career. He wanted the security and the opportunity," Gillespie said. "He just wanted his family to be proud of him. We are a very close family. We went to church and prayed for him every night, all of us."

"He wrote us to pray for him. He said he thought God sent him there for a purpose," said Ortega's sister. "He said he'd never seen so much hardship as they have in Lebanon--children without clothes, without parents, without food. He said maybe God put him there to help those children."

Both men were eager to leave Lebanon, relatives said. As one put it, "I guess everybody felt that way."