Right on Time by Vincent V. Cava

The woman in the shower was already dead when he found her.

A stalker had spent weeks memorizing every detail of her routine—7:30 AM wake-up, 8 AM coffee, 11:45 AM lunch at her desk except Wednesdays when she met the woman from HR—all so he could break into her townhouse while she showered. He had done this eight times before. He never left clues or called cards; he wanted none of the fame that trips up most serial killers. He only wanted to torture and kill as many "stuck-up skanks" as possible. "Getting arrested would ruin all the fun, and he'd barely just begun to play."

But when he twisted the unlocked bathroom door open at 10:58 PM, the shower was running with no sound of splashing or singing from behind the opaque beige curtain. He jerked it back. The woman was there, eyes wide with terror, but she could not scream. She was already dead. Someone had mangled her with a knife, sliced off each of her toes and fingers, carved gashes into her legs and stomach, and cut out her heart—leaving it next to the drain like a "blood soaked jellyfish." He had not planned for this.

Then he saw the mirror. A message was smeared across it in crimson letters: Right on time.

The killer had left it for him. While he had been stalking her, someone had been stalking him. While he planned her death, someone planned his.