Schalke ultras asked for the Borussia Dortmund bus attacker to be freed

Schalke's victory at Borussia Dortmund, which leaves Dortmund's title hopes hanging by a thread, was overshadowed by a placard which was shown by a part of the away support.
"Freedom for Sergei W.," it said. The man they are referring to is the person responsible for the attack on the Borussia Dortmund team bus in April 2017 prior to the Champions League tie with Monaco. He was sentenced to 14 years in prison.
Sergei W. placed a homemade bomb at the start of the bus' journey, which he detonated from a distance as he himself admitted during the trial. The man's objective was to cause as much harm as possible, according to the public prosecutor and he also took into account that he could have caused deaths and many more injuries.
April 27, 2019
At the end of the game, Marc Bartra, one of the players most affected by that incident, criticised the attitude of the Schalke fans on Twitter.
"Intolerable, unacceptable and sad. I hope the relevant authority takes suitable measures as a result of this incident. One thing is rivalry in football and another thing is to ask for a person who put 28 people's life at risk to be freed," he wrote.
April 27, 2019