EDITOR'S NOTE: Soledad reports from Newtown, CT on Monday, Jan. 14th, to report on how residents are coping one month after the shooting at Sandy Hook Elementary. Starting Point 7aET.
From CNN National Correspondent Susan Candiotti and Ross Levitt
One month after the Sandy Hook tragedy, investigators remain hard at work analyzing evidence and looking for a possible motive.
It will be May at the earliest before a final report is complete, according to police.
Adam Lanza was wearing ear plugs when he shot and killed 20 children and 6 adults at Sandy Hook Elementary last December 14th.
"We have no idea why," Connecticut State Police Lieutenant Paul Vance told CNN. Investigators may never know, he added.
Shooters at gun ranges often wear ear protection to muffle noise. The Bureau of Alcohol, Tobacco, Firearms and Explosives says the shooter and his mother did target shooting at gun ranges over the course of several years and went to at least one range together. Lanza fatally shot his mother, Nancy Lanza, at their home before he went to the school that day.
Vance also confirmed the shooter used "several" high capacity magazines, each carrying 30-rounds during the course of the mass murder. Each magazine for the AR-15 style semi-automatic made by Bushmaster was only partially used. Vance says the killer reloaded time and again. Investigators have been working to determine whether the gun jammed or whether Lanza had another reason to reload repeatedly.
Investigators would not say how many bullets were fired or exactly how many magazines were used.
About a week ago, authorities returned control of Sandy Hook Elementary school to Newtown. A barricade prevents outside traffic from driving past the school.
It remains shuttered.
Vance told CNN the shooter's home also is no longer an active crime scene.