meggy is the killer

"I think Oliver did it."

I do too. Oliver had access to a lot of inside info. Plus we do not know his
whereabouts around the time of Wes's death.
Even when he arrived at the scene, he seemed more nervous
than he should have been. He acted as though he knew something
about the murder/fire and reacted very suspiciously
when the fireman announced another body was found in the house.

He probably found out about Wes's immunity deal, as well as,
his, AK, and K5's connection to Sam's death. In fact, Oliver may be working for
Hannah (Sam's sister) and ADA Atwood, or both.
Perhaps, they have something on Oliver which forces him to do
their bidding. The problem though is he fell in love with Connor,
and looks up to and appreciates working with Annalise, so he feels conflicted.