Two officers from the Police Transport Command had parked in a carpark of a shopping centre on North Terrace about 7.20pm, when they were approached by a man.
Police will allege the man produced a knife and ran towards them, threatening the officers.
Shots were fired by police during the confrontation, with the 40-year-old man sustaining a wound to the leg.
He was taken to Liverpool Hospital under police guard where he underwent surgery and remains in a serious but stable condition.
The man has been charged with two counts of attempted murder, two counts of armed with intent to commit indictable offence, and two counts of assault police officer in execution of duty without actual bodily harm.
Investigations continue.
