Morbid curiosity most likely had me on a watchlist already, but I'll know for certain when the FBI knocks down my walls.
Here's a method: Stealing chemicals from an academic science storage room, then using it to poison someone. Put their corpses in the storage room, and make lines of the chemicals to make it look like a junky died trying to snort chemicals for a quick high.
Or you can stab someone to death (For the sake of academic convenience, with a sharpened ruler shiv) and bury them under the bleachers. More often than not, grass does not grow under the bleachers, allowing plenty of dirt space for stealthy burial.
This one is more psychologically demanding, but you can have the character secretly ruin the relationship between two people if one of them has extreme mental illnesses. Strangle the sane one and bury them in the insane one's yard, then strangle the insane one and hang the corpse in their room. For a couple of days, it will look like a murder-suicide, buying you time for more evil shenanigans. Make sure to include the location of the sane one's corpse in the fake suicide letter (or just the fact that he was killed to buy even more time for your character).
I have more, but I hear someone knocking on my door, and it does not sound like girl scouts or Mormons.