When a mother and child are shot, every police detective knows the husband is responsible at least half the time. When he runs off to another country under such suspicious circumstances, instead of sticking around to help solve the case, it's 99% certain the dirtbag did it.
The only scenario I can see under which he didn't do it is if it was a retribution killing for the e-bay scams and he doesn't want to go back to be killed himself (?)