Random in Death (In Death 58) by J.D.Robb

In this crime thriller from #1 New York Times-bestselling J.D. Robb, a small and easily concealed weapon wreaks havoc, and the killer is just a face in the crowd.
Jenna’s parents had finally given in, and there she was, at a New York club with her best friends, watching the legendary band Avenue A, carrying her demo in hopes of slipping it to the guitarist, Jake Kincade. Then, from the stage, Jake catches her eye, and smiles. It’s the best night of her life. It’s the last night of her life.
Minutes later, Jake’s in the alley getting some fresh air, and the girl from the dance floor comes stumbling out, sick and confused and deathly pale. He tries to help, but it’s no use. He doesn’t know that someone in the crowd has jabbed her with a needle—and when his girlfriend Nadine arrives, she knows the only thing left to do for the girl is call her friend, Lieutenant Eve Dallas.
After everyone on the scene is interviewed, lab results show a toxic mix of substances in the victim’s body—and for an extra touch of viciousness, the needle was teeming with infectious agents. Dallas searches for a pattern: Had any boys been harassing Jenna? Was she engaging in risky behavior or caught up in something shady? But there are no obvious clues why this levelheaded sixteen-year-old, passionate about her music, would be targeted.
And that worries Dallas. Because if Jenna wasn’t targeted, if she was just the random, unlucky victim of a madman consumed by hatred, there are likely more deaths to come.