Paradise beverage bar

Tobias James's mother, Anne James, was killed. Four suspects were identified by police after an investigation: a butcher, an engineer and his wife, and a jealous woman.
But her killing goes deeper than that. Tobias and his father are the targets of weird happenings surrounding the appearance of three guys in disguise. The situation becomes extremely convoluted and difficult.

One murder, two sets of suspects, and two reasonable theories. Who is at fault?