A Manhattan judge declared a mistrial Monday in the manslaughter trial of an undercover policeman who shot unarmed African art restorer Ousmane Zongo in a storage warehouse two years ago.

State Supreme Court Justice Daniel FitzGerald ended the trial after jurors sent their second note saying they were unable to decide unanimously the guilt or innocence of Officer Bryan Conroy in Zongo's death. They had sent the first note late Friday.

"We have thoroughly examined the facts and charges, and no further deliberations will resolve our differences," the jurors' second note said.

Conroy was charged with second-degree manslaughter for fatally shooting Zongo on May 22, 2003, inside Chelsea Mini-Storage on West 27th Street. Conroy, 25, would have faced up to 15 years in prison if convicted.

Conroy's lawyer, Stuart London, said he and prosecutors met with jurors for about 35 minutes after FitzGerald declared the mistrial.

He said jurors told them "it all came down to justification," whether Conroy was justified in shooting when he did.

London said it was unfortunate the jury did not reach a unanimous decision but it was clear that the prosecution did not prove its case beyond a reasonable doubt. He refused to divulge publicly what the jurors reported as their final vote.

The Manhattan district attorney's office will retry the case, spokeswoman Barbara Thompson said.

The judge ordered all the parties back to court on April 7 for motions and discussion of the likely retrial.

The president of the Patrolmen's Benevolent Association, Patrick Lynch, turned aside a question about whether the defense won.

"There are no winners or losers in this," he said. "This police officer had to do what no police officer wants to do."

The courtroom was crowded with police officers in civilian clothes, behind the defense table, and supporters of the Zongo family, behind the prosecution table. There was little audience reaction when the judge declared the mistrial and dismissed the jury.

Zongo's wife, Salimata Sanfo, said later through an interpreter that she has confidence in God and the jury system and believes truth and justice will be served soon.

Sanfo said she has no ill feelings toward police in general -- only against Conroy, because "he is a killer."

The trial was the first involving a city police officer in a fatal shooting since Amadou Diallo, also an unarmed West African immigrant, was infamously gunned down in the Bronx six years ago.

With no eyewitnesses and scant physical evidence, Conroy's grand jury account -- he testified that Zongo twice tried to seize his gun -- became the most important evidence in the case. The jury heard it once during the trial and again during deliberations.

Conroy said he first saw Zongo, 43, while guarding a bin of counterfeit CDs that police had seized on the third floor of Chelsea Mini-Storage. Zongo, father of two and a native of Burkina Faso who spoke little English, worked on that floor repairing African artifacts.

When Zongo stepped into the main corridor to turn on a light, Conroy -- disguised in his father's postal uniform -- drew his gun, aiming it at Zongo.

The officer, who said his police badge was pinned to his shirt front, said Zongo came toward him and tried to grab his gun but then turned and ran.

Assistant District Attorney Armad Durastanti ridiculed Conroy's account and said, "Mr. Zongo was not armed. He was not involved in any criminal activity. He was not a threat to Conroy or to anyone else."

But defense lawyer London said Conroy, a police officer since September 2000, fired only after Zongo tried to disarm him in "a life and death struggle."

Durastanti told the jury there were no powder burns indicating close shots, nor any trace hair or fiber evidence indicating the two had struggled with each other.

Zongo, shot four times with at least two of the shots in the back, died hours later at a nearby hospital.

Members of Zongo's family have filed a $150 million federal lawsuit against the city and Conroy, alleging the officer violated Zongo's civil rights by killing him.

Diallo was shot to death at his apartment building on Feb. 4, 1999, by four officers who said they mistook his wallet for a gun.

The officers, who said they wanted to talk to him because he fit the description of a rape suspect, were acquitted of state criminal charges in a February 2000 trial.