Elizabeth Prada of The End Times tells us what happened:
https://www.youtube.com/watch?v=XtjqIAiYOfo
On Sunday, August 16, an intruder wearing a backpack mounted the pulpit at John MacArthur’s Grace Community Church while Dr MacArthur was preaching the Sunday morning service, put his fingers in his lips and emitted a piercing whistle, pointed his finger at the pastor and began shouting that he had a message from the Lord to deliver to him.
The man, a Scottish “evangelist,” was angry that Dr MacArthur had preached in the past that the charismatic gifts have ceased, an interpretation termed “cessationism.” This biblical teaching was most recently delivered at the Strange Fire conference at Grace Community Church two years ago. That conference was a much-needed response and rebuke to the Charismatic movement which claims that Jesus delivers personal revelation to individuals today in the form of the temporary sign gifts of prophecy, tongues, interpretation of tongues, and also that people can and do perform miracles like raising people from the dead and healings, as the first century apostles performed.