Washington (CNN) A Justice Department report found "serious deficiencies" in the Philadelphia Police Department's use of force, finding about 15% of officer-involved shootings were of unarmed suspects who were mistaken for being armed.

Between 2007 and 2014, there were 394 officer involved shootings in the Philadelphia Police Department, despite a drop in violent crimes and assaults on police officers. The report found that 49% of these incidents were the result of "threat perception failures," or movements which led police to believe a potential suspect had a weapon such as reaching for their waistband, but turned out to be unarmed.

A majority of the other officer involved shootings included reports of physical confrontations related to suspects allegedly grabbing for officer's weapons.

But the assessment also found that Philadelphia police officers do not receive the sufficient training required to de-escalate potentially violent confrontations. For some recruits, this training has been nothing more than lectures.

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