New Jersey police are seeking a "person of interest" in a knife-stabbing attack in Newark that left three people dead and three others injured, many of them family members.

Acting Essex County Prosecutor Carolyn A. Murray said at a news conference after the attack Saturday afternoon that police are seeking a 26-year-old man in the case.

She said he already was wanted on charges of sexual assault and aggravated assault for an unrelated incident on Oct. 9. He has not been charged in Saturday's stabbings.

An 8-year-old girl, an 11-year-old boy and a 23-year-old woman were killed. Three others, a boy and a girl, both 13, and a 29-year-old woman, were in stable condition at a hospital.

Newark Mayor Ras Baraka called the attack "one of the most tragic and savage" he's seen. The mayor pleaded for anyone with information to come forward, NJ.com reported. "We have to get him immediately before he hurts someone else," he said. "As long as he's on the street, nobody is safe."

The mayor said, "This is probably one of the most tragic and savage situations that I've seen in a very, very long time here."

Essex County's major crimes task force and Newark police are investigating the attack.

Police have offered a $20,000 reward for information leading to an arrest.