An enthusiastic crowd of over 900 people celebrated on Sunday afternoon with Richmond County district attorney-elect Michael McMahon and his family, in what was billed as an "inauguration ceremony" in the packed gymnasium of the Spiro Sports Center at Wagner College on Grymes Hill.

Guest speakers included U.S. Sen. Charles Schumer and Mayor Bill de Blasio, who shared the stage with Public Advocate Leticia James, current and former Staten Island elected officials, judges, and Island NYPD top brass, among many others.

McMahon will begin duties as district attorney on January 1, 2016.

His official swearing-in is set for Tuesday, Dec. 29, at 10 a.m. at Borough Hall.

'GONNA KEEP THIS COMMUNITY SAFE'

Keynote speakers at Sunday afternoon's event were Sen. Charles Schumer and Mayor Bill de Blasio.

"Mike McMahon got here the old-fashioned way -- he earned it," said Sen. Schumer to thunderous applause. "He's gonna keep this community safe."

Mayor de Blasio, who received a standing ovation when he took the mic, recalled that he and McMahon served together on the City Council.

"I saw him so many times ahead of the curve," said de Blasio. "He had the ability to see what's needed and look over the horizon and do something about it."

De Blasio also cited the Island's "heroin scourge," terming it "a challenge we have to take on."

And then came this pledge from the mayor to McMahon: "He has an open door and an old friend at City Hall."

STOP MINDLESS DRUG DEATHS

In McMahon's inaugural address, he declared: "We proved the press and pundits wrong and the people right."

Explaining his agenda as incoming district attorney, McMahon pledged to "stop the mindless death of young people to the scourge of drugs," and prosecute the dealers.

He also pledged to "put an end to the shootings and get the illegal guns off the streets," and "bring safety to the battered," among other issues.

Then, turning to de Blasio, McMahon said this:

"Mr. Mayor, let us resolve that Staten Island gets it fair share of resources."