Shadowrun: Chaser. Shadowrun Novella, #17

STREETS ON FIRE. A vicious magical attack on a street gang isn't normally a case paranormal P. I. Jimmy Kincaid would pick up. But when a fellow private eye asks him to look into it, and he learns the gang was doing a charity run for a church-a church Jimmy knows quite well-when they were attacked, his professional curiosity is raised. His investigation quickly leads to a tangled maze of clues and dead-ends.
Someone-or something-is prowling the streets of Puyallup, looking to incinerate whoever crosses their path. And Jimmy's got to find them-and stop them-before the entire neighborhood goes up in flames. But whoever's looking to light innocent victims on fire made one mistake-they're doing it in Kincaid's backyard. And Jimmy has never taken kindly to trespassers.