Updated from Sept. 7

Washington Mutual

(WM) - Get Report

announced early Monday a shakeup of its top brass. Chairman and CEO Kerry Killinger is out, and taking his place is WaMu outsider Alan Fishman.

The executive change, first reported Sunday night on the

The Wall Street Journal's

Web site, initially sent shares of the Seattle thrift soaring in premarket trading Monday. The stock opened up 19.4% at $5.10 on a gap higher, but recently shares reversed and were trading down 42 cents, or 10%, at $3.85.

Fishman is chairman of Meridian Capital Group, a commercial mortgage brokerage firm, and a former COO of

Sovereign Bank

(SOV)

, a Philadelphia thrift he left in 2007.

Killinger joined WaMu in 1982 and worked his way up to the CEO position in 1990.

WaMu lately has been struggling with a large exposure to some of the riskiest mortgage products so popular during the recent housing boom, making the firm a

bellwether of sorts for the mortgage crisis

. The Seattle thrift reported a

huge second-quarter net loss of $3.3 billion

in July.

"I intend to hit the ground running here in Seattle with a focus on building on WaMu's strengths, addressing its weaknesses, and returning the company to profitability as quickly as possible," said Fishman in a company statement announcing his appointment.

"We believe Alan Fishman is the ideal executive to succeed Kerry Killinger and lead WaMu through its current challenges," said Chair of the Board Stephen Frank. "Alan has had a distinguished career in many aspects of the financial services business and brings a unique combination of in-depth industry knowledge, an entrepreneurial approach, and strong management skills that make him the right choice to be CEO of WaMu at this critical juncture."

This article was written by a staff member of TheStreet.com.