Robert Weir, 31, and Morag Campbell, whose six-year-old son Stewart is a pupil at the school described what happened after they were taken by ambulance into the grounds and kept in a room with 20 other parents.
"No one was told anything. They were completely falling apart," said Mr Weir.
"It seemed like an age before anything happened. Then someone came into the room and called out four names. One of them was Stewart. We were ushered into another room and I thought he was dead.
"We were told that Stewart had been hurt but no one could tell us how badly. Obviously we thought the worst."
Mr Weir and the other three sets of parents were instructed not to go back into the room beside the other parents. "They said they didn't want to alarm other people who didn't know what condition their kids were in."
Mr Weir and Ms Campbell were then taken under police escort to Falkirk Royal Infirmary, where they found out that their son had suffered pellet wounds in his leg.
"We saw him in the ward and he's really scared. I don't think he realises the extent of it.
"We'll have to keep a close eye on him for a few days but I think we'll get him home once his leg has been cleaned up.
"We just think of ourselves as very lucky," said Mr Weir. "I just wish we could turn the clock back and this has never happened. Our hearts and our deepest sympathy go out to all the other parents who may have lost their children. We know so many of them and it could so easily have been Stewart."
He went on: "The atmosphere in that room with 20 other parents was absolutely mind-numbing. No one was told anything. It seemed that the only ones that knew what had happened to our kids were the police and they weren't saying.
"The worst part was hearing Stewart's name called out. Morag and I obviously thought these were the kids that had been murdered. When we were taken out of the room we were told that our son and three of his friends were hurt. But that was all they could tell us. They couldn't say how badly or anything.
"I really don't know what the procedure is when dealing with a situation like this, but there were people in that room absolutely beside themselves, that knew nothing.
"I think three hours is an awful long time before the parents were given information and I think people should have been told a lot sooner.
"But who knows how to deal with an incident like this. It is so out of the ordinary.
"Morag is shattered. There's just no other word for it. But at least we still have our wee boy."
Another parent, Brian Owen, spent more than two hours at the school collecting his young son, who was, it turned out, unharmed.
As he left, he said: "I am absolutely devastated. You never think it is going to happen to you. Parents are very upset now and very concerned. All our thoughts are with the parents whose children have been killed or injured. I am lucky because my children are okay."
Mr Owen described the atmosphere at the school as "extremely tense". He said that parents were arriving and giving their names to police which were being matched up with children's names. Those parents who were bereaved were being taken to a separate place.
One parent, Mohammed Zahid, described how he rushed to the school after being told about the shooting.
He was terrified his daughter Suna, 5, had been involved but after rushing to the school it emerged she had been kept at home by her mother due to illness.
"I was so relieved I couldn't believe it. She is in that class and could have so easily been killed," said Mr Zahid.
Holding his other daughter Huma's hand, he said: "I just feel that I am one of the lucky parents."Reuse content