The terrorist group, ISIS, is now claiming responsibility for that horrific stabbing attack in Germany. And word just coming in that there has been a second arrest. Police raiding a refugee housing complex near the scene of the attack. At least three people were killed, several others injured, the incident taking place at a festival in a Western city. Late details from ABC's Maggie Ruheley.

Tonight, an urgent manhunt now underway in Germany for the person authorities say is responsible for a violent stabbing in the city of Zolingen Friday night. Isis now claiming responsibility for the incident, which left at least three people dead and eight more injured. The city's mayor saying, Last night, our hearts were torn apart. We in Zolingen are full of horror and grief. The emergency calls coming in just after 9:30 PM local time. The unidentified individual attacking people with a knife in the middle of the crowded Festival of Diversity, commemorating the city's 650th anniversary. An organizer at a stage nearby, urging festival goers to keep calm but also your eyes open because the perpetrator is on the run. The crime scene cordoned off. Forensics teams searching the area for evidence. The attack occurring in the audience in front of this stage. The lights above it still operating today. As mourners gather nearby, a growing memorial of flowers and candles honoring the victims. Two men, ages 56 and 67, and a 56-year-old woman did not survive. Police announcing a 15-year-old is now under arrest. They say they don't believe he was the attacker, but suspect him of knowing about it in advance.

Tonight, a police operation underway at this refugee housing complex. After they say they received a tip in the case, authorities making a second arrest there. Germany's Chancellor, Olaf Scholz, speaking today. Saying, We must never accept this in our society. We must do everything we can to investigate and prosecute the concrete offenses, but also do everything we can to prevent such things from happening again. And, Whit, while ISIS has claimed responsibility, it's still unclear exactly how closely tied the attacker may have been to the group. Police say they're working to determine a motive, and right now are urging people to stay vigilant.

Whit. Maggie Ruyly for us tonight. Thank.