A "murder-suicide" is a terribly convenient crime. Witnesses? All dead in the murder part. Perpetrator? Dead in the suicide part. All wrapped up, close the case, move along.
Interesting that the police are "not ruling out anything suspicious" - I read that as leaving the door open, CYA style, in case a bigger fish comes along and wants who-ever may have set this up. Then they'll "discover" some new evidence/lead/witness ...
Yes - interesting...