Scottish football authorities have begun an investigation after Celtic manager Neil Lennon was attacked by a fan at Tynecastle on Wednesday.
After Gary Hooper scored his second goal in the 49th minute, a supporter came out of the main stand and made straight for Lennon, sparking a fracas which also involved first-team coach Alan Thompson, police and stewards.
The intruder was marched up the tunnel by police and arrested, but Scottish Football Association chief executive Stewart Regan and his Scottish Premier League counterpart Neil Doncaster will now meet on Thursday to discuss how the incident was allowed to occur.
Regan said: "Clearly this kind of behaviour from supporters is wholly unacceptable.
"The safety of players, club officials and match officials is paramount on or around the field of play, and this clear breach of security is a matter I will be discussing with SPL chief executive Neil Doncaster."
Doncaster added: "The SPL deplores the actions of the individual involved. This type of behaviour has no place in Scottish football.
"The SPL will undertake a full investigation and will be reviewing reports from the SPL match delegate, match officials, the police and the clubs."
It is the latest incident to involve Lennon in a season in which he has had bullets sent to him in the post and a parcel bomb intercepted, as well as having to live with round-the-clock security.
Lennon's assistant Johan Mjallby admits he would not blame Lennon for walking away from the game in Scotland.
Mjallby said: "He is a strong character, he has coped with much. The backroom staff are desperate for him to continue but no one could blame him if he decided not to.
"I would never blame him whatever he does. I'm shocked and Neil must be even more afraid. What if he (the supporter) had something in his hand?
"But it is too early to say how Neil will react. I am shocked myself, I see it on television all over the world but I haven't seen it myself.
"We all have to look into this, a manager should be secure inside a football ground."
Hearts manager Jim Jefferies also believes Lennon might get fed up with the game if the problems continue.
He said: "For what he has had to contend with, I wouldn't blame him for walking away."
As peace was being restored in the technical area, trouble flared in the Celtic section of the stadium with fans appearing to fight with police and stewards.
A police spokesman said: "A number of incidents took place during this match, including some violent disorder.
"Lothian and Borders Police will fully investigate all of the incidents that occurred at the match and will work closely with both football clubs and the SPL."
Hearts have also launched an investigation and vowed to give their full co-operation to the authorities.
A club statement read: "An investigation into events which took place in the second half of the game against Celtic is now under way.
"Hearts is a club which prides itself on its 'Football for All' policy and these sorts of actions have no place in the game of football.
"We will give our full support to the stewards and police authorities in the ensuing investigation into the events at the match."
