The woman, who was on duty at the entrance to the new headquarters of the Paris police in the 17th arrondissement, was shot in the head by her 28-year-old colleague.
“This is a stupid drama that has just ruined two lives,” a senior police official told Le Parisien newspaper.
The officer who fired the gun was placed in detention after the incident on Sunday at the police headquarters in the 17th arrondissement of the French capital.
The Paris prosecutor and the head of the Paris police force went to the scene of the incident on Sunday.
The prosecutor's office has opened an investigation into the affair which will be conducted by the IGPN, the body that investigates police abuses.
It's not the first time in France that an armed police has officer has accidentally shot dead a colleague.
Two years ago an officer in eastern France accidentally shot his colleague in the chest while he was checking his weapon.