Can you just imagine?? Your boss, his wife, child and housekeeper have just been held captive, and brutally murdered. And the house set on fire. And you are, without knowledge, delivering the ransom money.
I would be a basket case!
That's what I am thinking. Sounds like police suspected him right away and started questioning him right then and there.
Then they questioned him again, there were discrepancies between stories, and pronto, he is accused of lying.