Mr. Donnelly's departure leaves housing commissioner Valerie Biscardi as the only commissioner appointed in Town Supervisor Brian Foley's first term remaining in their original position.

Mr. Donnelly attributed his departure to a "highly charged environment" the past two months, which he said included constant rumors of his being replaced as the head of economic development, a job he has held since 2006, the first year of the Democratic Foley administration.

"I've seen a lot of past commissioners fired with not a lot of notice, sometimes less than 24 hours," Mr. Donnelly said. "It was very abrupt and I did not want that to happen to me. I had an offer I'm excited about and I took it."

Next month, Mr. Donnelly will join the not-for-profit Long Island Forum for Technology, where, as a director, he will lead work-force development initiatives.

Mr. Foley called Mr. Donnelly's departure "another major blow to Brookhaven."

"The town has lost another very talented public servant," Mr. Foley said.

The supervisor was expected to make a recommendation to the Town Board at Thursday's work session, which occurred after press deadline, on how he thinks the town should move forward with finding a replacement for Mr. Donnelly. He was expected to recommend four executive recruiting companies to the board, in hopes that a national search be conducted to find the next economic development director.

Councilman Tim Mazzei, the Town Board majority leader, met in June with Islip economic development director Bill Mannix about the possibility of replacing Mr. Donnelly. Another rumored possibility to head economic development was former town supervisor candidate Robert DiCarlo, but Mr. Foley said Tuesday that officials from the Brookhaven Industrial Development Agency, which pays more than one-third of the economic development director's salary, nixed those plans.

"We can't have the usual cast of characters," Mr. Foley said, noting the importance of the position in a rough economic climate. "We need to conduct a serious search."

Ultimately, the hiring of the next director of economic development in Brookhaven is up to interim planning commissioner Brenda Prusinowski, since economic development is now a division of the planning department. Mr. Donnelly's replacement is not subject to Town Board approval. Ms. Prusinowski said she could not comment on what course of action the town would take to hire Mr. Donnelly's replacement because it is a personnel matter.

Attempts to reach Mr. Mazzei for comment before presstime were unsuccessful. His spokesperson, Frank Tassone, did leave a telephone message saying, "We wish Ray well."

While Mr. Donnelly said he is excited about opening a new chapter in his career, he did express regret about leaving Brookhaven. He pointed to the town's improved bond rating, which he said can be partly attributed to the supervisor's making economic development a "strategic part of the town's growth," bringing the Caithness Power Plant to Brookhaven, and an expanded approach to hiring within the town's Empire Zone as the finest successes of his time with the town.

"He set the bar high," Mr. Foley said.