Mary Blake, a supervisory assistant, and PE teacher Eileen Harrild, were both with Gwen Mayor and her class of 28 when Hamilton, clad in black, opened fire on March 13. He killed 16 five and six-year-olds and Mrs Mayor before shooting himself.

Their evidence provided a dramatic opening to Lord Cullen’s inquiry which will attempt to draw lessons from Britain’s worst mass murder.

In a written statement that was read out to the inquiry, Mrs Blake gave a harrowing account of the slaughter and revealed that Mrs Mayor had only intended to stay a few minutes in the lesson as she had been called to a meeting that morning.

Mrs Blake was shot in the head and legs. She described how Mrs Harrild first told the children to warm up, and then called them to her. They were standing close to the door when the gunman appeared.

“I think I was standing. I remember I looked towards the door. I saw a dark figure. I think Mrs Mayor was standing when he came in. Then I think Mrs Mayor was on the floor. The children were screaming.

“The dark figure was just inside the door, in dark clothing and he had some sort of headgear on. I was then hit and remember my head hurting. I realised something terrible was happening.

“I fell to the ground and he continued shooting. He had both arms up and he was pointing the gun all around and shooting constantly. I could hear the children screaming. It was so loud the screams seemed to be inside my head. ”

Mrs Blake then made her way to an open store area in the corner of the gym, following Mrs Harrild and four or five dazed and injured children.

“I was in pain from my head and legs. I thought this was the end. I thought if he came round the corner we would all be dead. One child kept saying: ‘What a bad man.’ They all kept saying they were sore,” she said.

She said she wanted to pull the gym mats round the children to protect them, but was too weak.

“I could hear the children wailing. The shooting stopped, then started again for a few seconds. I felt so helpless. I could not move.”

Then silence fell on the gym.

Other teachers then arrived. “One was in a terrible state and kept asking, ‘What can I do?’. She could not do anything,” Mrs Blake said.

PE teacher Eileen Harrild, 43, told how she was shot in the arms and chest, and tried to escape to an open store area with some of the children.

“The children were amazingly calm. They were very surprised and they were very good when we tried to silence them. We just put our fingers to our lips and they were very quiet. We did not want him to come back into that area.”

She said the shooting lasted three to four minutes as Hamilton moved around the gym, picking off the children.

Forensic scientist Malcolm Chisholm, a scenes of crime officer with Tayside police, said Hamilton arrived with four guns, two Smith and Wessons and two Belgian-made Browning pistols, and 743 rounds of ammunition. He used one of the Brownings to kill his helpless victims.

During police tests it was found that the 105 rounds fired by Hamilton could be discharged in as little as 50.4 seconds from the customised automatic.

Hamilton entered the school with apparent ease. His first shot was fired through the floor of the stage in the school hall and the second in a toilet wall in the corridor near the gym entrance. He then fired indiscriminately, walking around the gym before moving to an emergency exit. He then fired four shots towards the library and main entrance, injuring a teacher walking along the corridor.

He fired nine shots at a temporary classroom next to the gym, stepped back into the gym and discharged around six more bullets.

After that, he drew a Smith and Wesson from one of his four holsters, put it in his mouth and pulled the trigger.

Student teacher Duke Scott watched Hamilton’s final moments from an art class and was the first to alert other teachers that the killer was dead.

Several witnesses said that Hamilton’s attack was not only a frenzied act of madness, but a carefully planned murder.

He had attempted to isolate the school prior to the massacre, by cutting phone lines on a telegraph pole.

It transpired that Hamilton had cut off nearby houses, but fortunately had not affected the school’s one land line.

Detective Chief Superintendent John Ogg, who headed the investigation, said police got the first call at 9.41am and were at the scene nine minutes later.

The first shot was fired at 9.37am. Mrs Harrild was the first victim, followed by Mrs Mayor and then Mrs Blake. Hamilton then sprayed the children with bullets. He also shot twice at two boys walking past outside the gym.

In the aftermath of the slaughter, Mr Ogg spoke of the difficulties of identifying the tiny bodies strewn around the gym and he paid tribute to the teachers who took on the harrowing task. “They did extremely well. The headteacher and his staff did an absolutely unbelievable job because of the circumstances,” he said.

He said delays in informing parents were caused by confusion over the identity of victims who had been taken to hospital and those lying dead, because police had not taken names of the injured as they left the gym, which he admitted, in retrospect, should perhaps have been done. Also the register had not been taken that day and it was only later that it emerged that two children were absent.

Communication was hampered with Stirling Royal Infirmary because the school’s sole phone line was engaged by anxious parents, and attempts to use mobile phones were also hampered because the lines were jammed by the mass of journalists outside the school.

It was not until 1.30-2.30pm that parents of victims were finally told of their loss, because Mr Ogg wanted to be 100 per cent sure of the identities before releasing information.

Lord Cullen, who headed the inquiry into the Piper Alpha oil platform blaze, already has identified three issues relating to gun controls, school security, and vetting adults who work with children as areas where he expects to make recommendations following the inquiry.

The inquiry is expected to last for up to two months.