He had led boys as young, in his day, and seem them killed, which was why he kept putting Newt off. (2.62)
Call's biggest fear is that one of the young men in his group will be killed on the cattle drive. And it isn't the anxious thought of a paranoid father figure, either. That's partly because Call could never be considered a father figure, and partly because this is a very, very real fear.
Two worries seesawed in his mind: that he might get killed or that he might make a stupid blunder and displease the Captain. (11.49)
Humiliating himself in front of the Captain is a fate almost as bad as death in Newt's eyes. Perhaps he realizes that if he displeases the Captain too much, he will be out on his own, and it will be very hard to make a living.
"It seems too quick," he said. "It seems very quick, just to ride off and leave the boy. He was the babe of the family." (35.99)
Death waits for no one, and the cattle drive can't wait for death. As devastated as Allen is by his brother's death, the drive can't be put on hold for anything. It's not like it will bring Sean back if they stop moving on. Allen will have to grieve on the go.
"Well, Call, I guess they forgot us, like they forgot the Alamo," Augustus said.
"Why wouldn't they?" Call asked. "We ain't been around."
"That ain't the reason—the reason is we didn't die." (42.106-42.109)
Heroes are sometimes only heroes if they die. Gus and Call have stayed alive long enough to watch their reputations fade. But this conversation occurs way before we ever thought Gus would die. Maybe his hero status is cemented after his death.
Roscoe felt warm and sleepy and sat back down. It was like he was in a warm bath. (58.25)
This is one of the first deaths we get from the point of view of the person doing the dying. It's like going to sleep, right? In a nice warm bath? Perhaps this is McMurtry's way of softening the blow as Roscoe is brutally murdered by Blue Duck.
Roscoe was dead, Joe was dead, the girl was dead, and Ellie not found—maybe she too was dead. All he had to report was death and failure. (69.3)
Death and failure go hand in hand in Lonesome Dove. It's a high stakes world here, and to fail usually means to die, so death is often an indication of some kind of failure. It's not comforting in the least.
"I never expected to be fool enough to let them murder me. It's humbling. I lived through the worst war ever fought and then got killed by a damn sneaking horsethief. That galls me, I tell you." (72.79)
This is Wilbarger talking, reinforcing the sudden, unexpected death motif in the book. We'll see it again later when Gus is killed by an Indian's arrow. He never expected to get killed by an Indian, especially not in a land where they were no longer supposed to be living.
It was such a startling thought—that under him, beneath the long grass, were millions of bones—that Newt stopped feeling so strained. He rode beside Mr. Gus, thinking about, the rest of the night. (72.124)
Here we see Newt coming to terms with his eventual death, in a way. He realizes that eventually all things return to bones—even his friends, and even himself.
Then the screams stopped abruptly as Sean slipped under the water. (35.46)
This is the first major death in the book, and it happens suddenly, abruptly, and with no foreshadowing or reason behind it. Death is like that sometimes.
"Talk's the way to kill it. Anything gets boring if you talk about it enough, even death." (39.20)
Gus makes a good point here. Isn't that the reason any book is written about anything? To talk about it? And at least fool people into feeling okay about death?