Megan Hilty is mourning her pregnant sister, brother-in-law and niece

They died in a floatplane crash Sunday

Aircraft went down in Puget Sound in Washington

There were 10 passengers on board in the aircraft

Search of passengers recovered one unidentified female body

Crash occurred between Friday Harbor and Renton Municipal Airport

Lauren was pregnant at the time of the crash

Megan's sister , brother in law died in this crash

Reason of Crash is still unknown