There are lots of questions about the Reformation and the events which led up to it, but these are the ones which concern us most.
The upheaval which we call the Reformation had social and political elements, as well as theological. The Scottish Church as a whole had become notorious for corruption and the ordinary people lacked pastoral care. Priests assigned to carry out the liturgy were frequently deficient in basic learning and unable to read the services in Latin, let alone understand them. The population as a whole was being taxed, one way or another, to support clergy, and the friars of various orders were professional beggars, which added to the discontent. The "Beggar's Summonds" had specified the grievances of the people and copies had been fixed on the doors of the Friaries the previous year. Read the Beggar's Summonds here
There was also a dislike of the Queen Regent, Mary of Guise, through whom the political status of Scotland was too closely connected with France - to Scotland's disadvantage; and England now had the Protestant Queen Elizabeth.
At an early stage, the Burgesses and Town Council had declared themselves in favour of the Reformers, so Knox knew that, in Perth, he would be among friends. At this time, Perth was a walled city (not common in Scotland) and it could be defended if Mary of Guise chose to attack from her base in Stirling.
St.
John's was the Parish Church and the centre of the community. The
topic of Knox's sermon was the `sin of idolatry'. It seems that
following this, a priest decided to celebrate Mass, to which a young
lad voiced his objections. Thereupon the Priest hit the boy, the boy
threw a stone which broke the altar - and mayhem broke out.
According to Knox, it was not worshippers who went on the rampage, but the `rascal multitude' who went to the buildings of the Grey and Black Friars, broke in and carried off whatever they could find. It seems to bear an awful similarity to some inner city riots with which we are unfortunately familiar today.
Thus the Reformation gained momentum.