While there is no motive known for the man, he is reported to have walked along a beam high above the crowd, while fans shouted for him to come down, and Michael Oliver suspended the game. He spoke with both captains - Kasper Schmeichel and Ilkay Gundogan - with TV images showing that he was pointing out the masked individual, a 21-year-old who has since been arrested.
Police required the use of a helicopter to locate the individual, hence the delay.
Daily Mail