The Brief

A U.S. sailor has been declared lost at sea after initially being reported missing last month, according to the U.S. Naval Institute.

What we know:

According to the private non-profit military association , Jose Antonio Rivera Lynch IV, 19, a third-class aviation boatswain’s mate, was assumed overboard from the USS George Washington.

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The U.S. Navy and Australian Defence and Australian Border Forces launched search efforts in the Timor Sea on July 30.

What we don't know:

The U.S. Navy has not explained why Lynch may have gone overboard.

The backstory:

According to the institute, at 19, Rivera Lynch served in the Navy for just over a year.

A native of Middleburg, Fla.

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