Death Pact by Matt Hilton

This action-packed standalone novel follows two brothers who escaped a cult as children, now drawn into the dark web of a serial killer.
Not all angels are goodness and light; some are the most murderous creatures imaginable.
Former detective Nate Freeman seeks solitude as he recovers from the case that ended his career. Rescued from a religious cult in the US as a child, Nate now lives in the UK with no contact with his brother Will or other 'Children of Hamor' survivors. But when these survivors start turning up dead, skinned and marked with cult symbols, Nate is thrust back into danger.
DCI Openshaw, Nate's old boss, asks for his help to catch the serial killer obsessed with collecting the symbols branded onto the children's backs in the name of Berith, the Fallen Angel. As Nate reenters this deadly world, he faces mortal danger as one of 'the promised.' Meanwhile, the evidence points to Will as the prime suspect.
Nate must unravel the identity of the 'angelic' killer and save himself and his brother in a high-stakes race against time.