At a news conference on Monday, Chief Shea, a son of working-class Irish immigrants who grew up in a cramped apartment in Sunnyside, Queens, recalled his early days as an officer in the 46th Precinct fondly. He had joined the department along with his brother and cousin.

“There was nothing better than walking out and just talking to people as you would interact with them day in and day out,” he said.

Chief Shea pledged to build on the work of his predecessor, Commissioner James P. O’Neill, when he takes over the top job on Dec. 1. He also said he would prioritize taking down gangs and getting guns off the streets.

Patrick J. Lynch, the president of the Police Benevolent Association, a union, welcomed Chief Shea’s appointment, describing it as a hopeful sign for rank-and-file officers, who Mr. Lynch says are in need of support from the top.

“We look forward to working with Commissioner Shea to combat the current anti-police atmosphere and make positive changes that will improve the lives of our police officers and every New Yorker we protect,” Mr. Lynch said.

Critics of the department were less enthusiastic.

Councilman Donovan Richards, a Queens Democrat who leads the Council’s Committee on Public Safety, described the incoming commissioner as a “personable individual whose heart is in the right place.”

But Mr. Richards said that Chief Shea’s appointment was a “missed opportunity to really diversify the top office” of the Police Department.