Aggressive screams during Kaczyński's speech. What happened there?

Tension in Piłsudski Square in Warsaw. During a speech by Jarosław Kaczyński on the occasion of the monthly Smolensk disaster, loud shouts of “Lie!” came out of the crowd. The president of PiS spoke of abroad agents, the German border and "subordination of Poland to external forces". The atmosphere was tense and political...