Release conditions were set for Mahanga's release last Saturday and included he have no contact with the victim's family and not enter the area north of Kaiwaka township, without prior written approval of a probation office.
He was also not to possess or consume alcohol or illicit drugs.
Kate McGrath, sister-in-law of Wowo, said it was an uncomfortable feeling knowing Mahanga had been released.
"Just because he has done his time it's not the end for us. We carry a life sentence."
She said the family had just found their feet and now they were dealt another blow. "It's a bit like an earthquake. You expect them but you just don't know how it's going to affect you or what devastation it's going to cause."
In June last year, Mahanga was denied parole for the third time after the board discovered he had been taking methamphetamine in prison. He denied using meth intentionally and explained his drink bottle was spiked by former gang associates. However he could not prove his claims and his security classification was increased to high.
Mahanga assaulted Patricia, after a 14-month relationship, in a house on Fairway Drive in Kamo in January 2013.