Sources close to the investigation blame a recently retired sergeant from the NYPD who lives nearby.
On his police scanner, he heard a call for a man with a knife, and took it upon himself to respond.
Theresa Kelly is the person who made the call to 911, after she says 21-year-old Anthony DiGeronimo jumped on the hood of her car and threatened her with a knife, and allegedly lunged at arriving officers, who shot and killed him.
Kelly says she tried to talk to the officers, but that retired sergeant unleashed a profanity laced tirade against her.
"And he threw me into my car. He kicked me into my car. He said, 'What don't you understand?' He put his foot up against my door and threw me into the car," Kelly said.
A few minutes later, sources say the retired sergeant spotted plainclothes Officer Geoffrey Breitkopf striding toward the scene with a shotgun at his side, pointing at the ground.
The retired cop allegedly shouted "gun", startling an MTA officer who shot Breitkopf.
Radio transmission tapes detailed the chaos that came next.
It isn't clear what, if any, laws the retired sergeant might have broken, the District Attorney's office will not say if it intends to charge him.
But, Theresa Kelly says a detective told her, the former cop had no business on that scene.
"He said he didn't belong here. He was a retired New York City policeman, and he said he didn't belong here," Kelly said.
Donations and funeral arrangements
In response to the outpouring of support of those seeking to send donations for the family of Nassau County Police Officer Geoffrey J. Breitkopf who was killed in the line of duty on March 12, 2011, donations can be made to the Geoffrey J. Breitkopf Memorial Fund, c/o Nassau County P.B.A., 89 E. Jericho Tpke., Mineola, NY 11501. Officer Breitkopf leaves behind a wife and two young boys.
Viewing and Funeral Service:
The public is invited to pay their respects at the Selden Fire Department Headquarters, 44 Woodmere Place, Selden, New York, on Wednesday, March 16 and Thursday, March 17, 2:00 - 5:00 p.m. and 7:00 - 9:00 p.m.
Funeral services for Officer Geoffrey J. Breitkopf will be held at St. Margaret of Scotland Roman Catholic Church, 81 College Road, Selden, New York, on Friday, March 18, 2011, at 12:30 p.m.
Interment will follow at Holy Sepulchre Cemetery, 3442 Route 112, Coram, New York.