There was a book, probably part of a series, that I read 10-15 years ago about a group of kids on a school trip who were accidentally exposed to chemical testing by the government. These kids grew up, and their children had powers/problems, so a secret government agency sent a killer to kill the adults and their children. The part that I remember the most was that two of the now-grown adults who had been exposed were being chased by the killer, and, while they agreed that they would never divulge the location of their own children, they could not promise that about the other person's children, so they killed themselves.
Crosscut by Meg Gardiner
Evan Delaney knew China Lake was a tough place to grow up. But she never knew how tough until now. She returns to the desert military base for her high school reunion, and learns that a number of her classmates have died young. Then, on the first night of the reunion, another one dies, this one savagely butchered. And she’s just the first. Someone has an axe to grind and Evan’s graduating class has something to fear.
From review on amazon:
...this time Evan discovers that something, or someone, is killing off her high school graduating class. More specifically, the targets were all part of a particular field trip at China Lake and Evan is part of a quartet who are being saved for last, which is not even close to being a good thing.