1089
Several police officers were treated for the effects of gas after the ensuing clashes -- a result , police said , of the demonstrators using self - defence devices .
 demonstrators: attacker; officers: target; devices: instrument
Given event type and trigger, please tell me the arguments of all the listed option. Output format is "name1: role1; name2: role2". 
Event type: attack 
  Option: victim, attacker, place, target, instrument 
Text: {0} 
Answer:
 demonstrators: attacker; officers: target; devices: instrument