Staten Island District Attorney Michael McMahon, at his swearing-in ceremony Sunday, vowed to lead the borough in what he described as a tough fight ahead against widespread opioid abuse, illegal guns and domestic violence.

He also called for stronger police and community relations.

“Let us resolve to build bridges between the brave men and women of law enforcement, and all the people of Staten Island of all races, ethnic backgrounds, genders, sexual orientation, religion and economic status,” he said at Wagner College, in Staten Island’s Grymes Hill neighborhood.

McMahon, a Democratic former congressman, defeated Republican Joan Illuzzi in a close contest for the top prosecutor seat, which was thrust into the national spotlight a year ago when a Staten Island grand jury declined to indict an NYPD officer in the death of Eric Garner. McMahon replaced Daniel Donovan, now a Republican in Congress.

McMahon did not mention the Garner case in his remarks.

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He called on Mayor Bill de Blasio’s office to provide Staten Island with “its fair share of resources,” including a full narcotics bureau.

“Let us resolve that we will stop the mindless death of young people to the scourge of drugs, to prosecute the dealers, to help the addicted when possible and to prevent this cycle from continuing,” McMahon said of heroin- and prescription painkiller-linked fatalities.

De Blasio, who earlier this month in Staten Island announced he was expanding the availability of a lifesaving medication that can reverse the effects of an overdose, also referred to the opioid crisis in his speech at the ceremony. The city’s leaders must band together to fight the “scourge of heroin” and take the response to “the next level,” he said.