Mr. Browne said the sessions next week were meant to reinforce training the officers have had, rather than provide additional instruction in the use of the Taser. Currently, 525 members of the Emergency Service Unit and sergeants throughout the department carry a Taser gun on their holsters. Mr. Kelly has so far balked at distributing the Tasers more widely. The guns are designed to incapacitate their target with a pulsating electrical current.

Chief Molloy, 47, who lives in Queens with his wife and two daughters, has had a wide range of experience since joining the department in 1982. He has served in about a dozen precincts, detective bureaus and narcotics squads.

In recent years, he has responded to some of the city’s most serious emergencies, including the deadly Staten Island ferry crash in 2003 and the explosion of a steam pipe in Midtown in 2007. He also helped direct special operations when the baseball player Cory Lidle crashed a small airplane into an East Side apartment building, and coordinated operations with federal and state agencies at the Republican National Convention, the department said.

Over the summer, Chief Molloy was on hand when climbers scaled The New York Times building. About 35 officers were needed to cordon off sidewalks and retrieve the climbers from the top of the building. Officers strained to communicate with the climbers and battled with strong winds as they coordinated the rescue efforts. Chief Molloy said at the time that such incidents prompted a major response and diverted needed resources from regular patrols.

In addition to earning a master’s degree in public administration from Marist College, Chief Molloy graduated from the F.B.I. Academy.

The Emergency Service Unit had been without a permanent commander for several months, Mr. Browne said. The former permanent commander, Inspector James Dean, has been on sick leave. When he returns he will become the executive officer of the department’s Special Operations Division.