Ridley was fatally shot in January by county police as he tried to break up a fight involving a homeless man.
In notices of claim, the family says White Plains and the county did not supervise the 39-year-old homeless man. The family also charges the county with "negligent and careless training" of its police officers and Mount Vernon with failing "to provide adequate training and supervision" to the officer.
Ridley was off duty when he confronted the man, who pulled his handgun from Ridley's waistband and it went off. Ridley retrieved the gun and was shot by county officers after he failed to respond to a command to put it down.
Last month, a Westchester County grand jury cleared the four officers of any criminal wrongdoing.
