Police said on March 8 that the suspect, whose name was not made public, acknowledged the stabbings of a 20-year-old Afghan male acquaintance and three members of a separate family.
The victims' names were also not released.
The suspect was detained shortly after the stabbing of the 20-year-old late on March 7 in the Austrian capital, police said.
Earlier in the evening at about 7:45 p.m. local time, he allegedly attacked three members of a family -- the 67-year-old father, the 56-year-old mother, and their 17-year-old daughter -- on the large shopping street of Praterstrasse in the center of Vienna.
Police said the father was in critical condition, while his wife and daughter remained hospitalized in stable condition. The injured Afghan man was also reported to be stable.
Authorities said the motive for the attack on the family was unclear. But they said the suspect told police he knew the Afghan man, saying he was targeted because 'he holds him responsible for his previous drug addiction.'
The suspect also said he was in a 'bad, aggressive mood and upset about his life's situation' when he committed the attacks, police reported.
Based on reporting by AP and AFP