I can't figure out the past participle of the verb 'irrompere': it seems to be a compound form of the verb 'rompere', past participle of which is 'rotto', but 'irrotto' sounds very strange to me. Is this some kind of irregular verb?
Lo Zingarelli reports that the past participle of irrompere is irrotto and says that other compound tenses are rarely used.
Treccani says that past participle and compound tenses are not used.
I would understand irrotto, since it recalls the past participle of similar verbs like corrompere (corrotto), rompere (rotto).
Personally, instead of saying la polizia è irrotta nel locale, bloccando ed arrestando quattro malviventi, I would say la polizia ha fatto irruzione nel locale, bloccando ed arrestando quattro malviventi.
It's irregular, you can use
aver fatto irruzione if you need to use it with past.
Irrotto doesn't exist (we are still talking about a language, tomorrow irrotto can be perfectly correct).