This is the 5539th most frequent Russian word.
полицейских
"Police officers" (plural form).
The word 'полицейских' is in plural, genitive case used as a direct object of the verb 'боялся' indicating fear of police officers.
Мальчик боялся полицейских.
The boy was afraid of the police officers.
The word 'полицейских' is used in plural, genitive case to denote possession or association with police officers.
В городе происходит собрание полицейских.
A meeting of police officers is taking place in the city.
Here, 'полицейских' is in the plural, genitive case used with the preposition 'благодаря' to indicate the assistance by police officers.