NORWALK, Conn. -- The Norwalk Police Department said Sunday "all possible theories" surrounding the death of a veteran officer last week will be investigated, after the medical examiner announced that autopsy results won't be available for weeks.

In a statement, Norwalk police said investigators are examining more evidence retrieved from the scene where 11-year veteran Matt Morelli died -- allegedly after an altercation outside of a housing complex.

The autopsy report proved inconclusive, and Norwalk police said it is awaiting results of physical testing from the scene.

They did not say what theories they are exploring.

Meantime, funeral arrangements for Morelli have been set, with a wake scheduled for Wednesday evening and a funeral and burial set for Thursday morning.

Morelli's death is shrouded in mystery. Sources told NBC 30 that there was an incident or argument outside a housing complex called Lubrano Place, leading to an exchange of gunfire between police and the shooter.

Officials said in a press conference that Morelli called in and indicated that he was stepping out of his vehicle. Backup officers responded within one minute and found Morelli dead, officials said.

Police blocked off several streets and were using dogs to search the area. Helicopters from the NYPD and the Westchester County Police Department assisted with the search of the area.

The flag at police headquarters was lowered to half-staff. Morelli was a veteran of the U.S. Marine Corps.

Officials said four Norwalk officers have been killed in the line of duty with the last one being in March 1982.

A tip line was created, and anyone with information regarding this investigation is asked to call 203-854-3111.