The bodies are those of a 53-year-old man and two women aged 52 and 21.
Six people were killed by the attacker in central Krakow. Fifteen others were injured.
The attacker was identified in the Polish press under the name Michal O.
This mourning, opened the day after the events, measures the gravity of an attack that occurred in the city center.
In addition to these six victims, three people were found dead at the attacker's home.
The authorities describe him as a young man.
Seriously wounded, he remained in critical condition on Sunday morning, according to the police spokesperson. According to the authorities, the suspect is"fascinated"by far-right ideas.