Police have arrested a 15-year-old boy in connection with a fatal knife attack in the western German city of Solingen.

The boy is not the main suspect, but is said to have known about the attack in advance.

The attack in Solingen on Friday killed two men aged 56 and 67 and a 56-year-old woman. German Chancellor Olaf Scholz called the attack a “terrible act”.

At a press conference on Saturday, police said terrorism had not been ruled out as a motive and that a nationwide search was underway for the attacker.

The 15-year-old involved in the case was arrested this morning after two women reported overhearing a conversation between him and a second person in which they discussed the attack, police said.

While he remains in custody, investigators are still trying to determine who exactly carried out the attack.

The suspect’s motive is unknown, but police say they cannot rule out the possibility that it was a “terrorist-motivated crime.”

According to the police, there was no specific terrorist threat prior to the festival and no large security zone had been set up.

Police Chief Markus Röhrl urged people not to speculate on social media and called on the public for more information.

Police also said they found “multiple knives” and are investigating whether any of them were involved in the attack.

The attacker is said to have “randomly” stabbed passers-by during a celebration celebrating the 650th anniversary of the industrial city of Solingen.

The situation on the scene was “very hectic” after the attack, making it difficult to find a perpetrator, police said.

Police confirmed that the attacker targeted people’s throats and necks.

German Chancellor Olaf Scholz said the attacker must be caught quickly and punished as fully as possible.

Interior Minister Nancy Faeser expressed her condolences and said security authorities were “doing everything they can to catch the perpetrator and determine the background to the attack.”

Solingen – a city in North Rhine-Westphalia, known for its steel industry – has about 160,000 inhabitants. It is located about 15 miles (25 km) east of Düsseldorf.

City authorities asked people to leave the Fronhof market area following the attack on Friday at around 10:00 pm local time (9:00 pm BST).

Mayor Tim Kurzbach said in a statement on Facebook on Friday evening: “Tonight we are all in Solingen in shock, horrified and very sad.

“We all wanted to celebrate our city anniversary together and now we have to mourn the dead and wounded.

“It breaks my heart that an attack has taken place in our city. I have tears in my eyes when I think of those we have lost.

“I pray for all those who are still fighting for their lives. Also my deepest sympathy for all those who had to experience this, these images must have been terrible.”