The harrowing details of how the Newtown massacre began

It is the repeating rituals that offer reassurance and tell us, as parents and children, all will be well. So it was on Friday at Sandy Hook Elementary School. Under blue skies, teachers waited outside at 9am as the first yellow school buses swung into the driveway to offload their excited, chattering cargoes. The children rushed through the doors of the front entrance and towards their classrooms to hang up their coats and get ready for the day.

Sharp at 9.30, those front doors were locked and the video system was switched on, all part of a new security system introduced by headmistress Dawn Hochsprung just weeks earlier. She had a teachers' meeting in a small conference room off the entrance hall to go to. Children cast in a Christmas nativity play started rehearsals in the cafeteria and elsewhere in the one-storey building teachers finished taking the register and began their classes.

But five miles away the rhythms had already been snapped. On Yogananda Street, an enclave of Sandy Hook dotted with large, newer homes on a rising crest, a woman wearing pyjamas lay dead in her bed, shot four times in the head, investigators say, by her 20-year-old son Adam Lanza, with whom she shared the house. And so a first question of so many. What had happened between mother and son? But it is where Lanza's rage led him next that beggars all comprehension.

Dressed in paramilitary-style clothes and bearing two pistols and a Bushmaster rifle, having left a shotgun in his car, he jumped in his mother's car and sped away. Lanza was heading for a school. Not any one, but Sandy Hook Elementary, happy refuge to some of the youngest souls of this community in the Connecticut hills, with years like 2006 on their birth certificates.

Lieutenant Paul Vance of the Connecticut State Patrol, the spokesman for the investigation, yesterday remained reticent about some of the details of exactly what occurred when Lanza reached his destination.

"Our goal is to answer every single question," he told reporters last night. "We have the best of the best working on this case."

But some things we do know. Lanza was not let into the school; he shattered the glass front door with blasts from the rifle. "He forcibly entered the school facility itself," Lt Vance said.

Those early blasts were enough to sound the alarm for everyone in the building that something bad was afoot. Through the front door, Lanza turned left and moved towards two classrooms of children in the first grade. But first, Ms Hochsprung and the school psychologist Mary Scherlach, rushed out of their meeting and attempted to intercept him. He shot them both with his rifle.

The first room he reached, where Kaitlin Roig was teacher, he walked straight by, preferring the class of substitute teacher Lauren Rousseau. Once inside, he began pulling on the trigger of the rifle with seeming awful accuracy. Fourteen terrified pupils were looking up at him – not one among them was spared, nor was Ms Rousseau.

Next he turned to the classroom of Victoria Soto, who had by then herded her pupils, aged just six and seven, into a storage cupboard. When he entered, she tried to divert him insisting her children were in the gym at the other end of the school, but it appears that six then tried to flee and the gunman killed them as they ran. And then he killed Ms Soto.

It was the arrival of the police, while Lanza was in the second classroom, that prompted him to turn the gun on himself. If they had not arrived so quickly, many more children may have been killed.

All of the 20 children and six adults who were killed in the attack suffered multiple wounds, according to coroners who did the autopsies. "I did seven myself with three to 11 wounds apiece," the Chief State Medical Examiner Dr. H Wayne Carver III noted. "Only two were shot at close range. I believe everybody was hit [by bullets] more than once."

The best estimates say the rampage lasted about 10 minutes and that Lanza fired hundreds of rounds of ammunition, with hundreds still remaining. By the time the police reached the school, the savagery was already done and Lanza lay on the floor, dead from a self-inflicted wound. They found two children still living but mortally wounded. Then it was time to find and lead away the survivors, many hiding in storage rooms, toilets, in one case in a music-room, its door jammed shut by xylophones.

The first two funerals of the child victims are due to be held today for six-year-olds Noah Pozner and Jack Pinto. While schools in Newtown are meant to reopen tomorrow, theirs surely will not. Indeed, it may never be used again, one official here admitted last night. Those reassuring routines were sundered on Friday and repairing them won't even begin until some of the questions are answered, if they ever can be.