KRAKÓW, Poland — Poland began two days of national mourning Sunday after a gunman killed six people Saturday in Kraków’s Main Market Square, one of the country’s busiest historic gathering places.

Police wounded and apprehended the 24-year-old suspect. Two officers were among those injured. Authorities reported that the suspect remained in critical condition.

Investigators also found three people shot dead at the suspect’s home in Ostrowiec Świętokrzyski. A prosecutor said the cases were likely connected and remained under investigation. Officials said they were examining possible extremist motives.

Poland’s president ordered national mourning for Nov. 8 and 9. Police also tightened security in busy parts of Warsaw following the attack.