(CNN) -- A review of police response to the massacre at Sandy Hook Elementary School has found that officers "responded to the scene rapidly, positioned themselves appropriately, and followed their department policy," according to a report by the Connecticut Police Chiefs Association.
The nine-page report analyzing the Newtown Police Department's response time and entry to the school during last December's mass shooting was written by a subcommittee of four police chiefs from the state.
"Our evaluation showed that the officers of the Newtown Police Department navigated the inevitable chaos created in the first few minutes of such a call, managed to piece together what was occurring, but were unable to intervene before the shooter took his own life," according to the report, which was released Thursday.
The review references a CNN report that said, "Police and other first responders arrived on scene about 20 minutes after the first calls."
CNN initially reported police arrived "within 20 minutes."
The committee had access to 911 recordings, dispatch tapes, first-responder and officer statements as well as other documentation. The committee report was released on the same week as audio recordings of 911 calls to police from the school at the time of the shootings.
The December 14, 2012, massacre left 20 first-graders and six school employees dead. The shooter, Adam Lanza, 20, shot himself and died in the school.
Newtown Police Department Chief Michael Kehoe requested the analysis after media reports indicated the response time was greater than Kehoe knew it to be, said Jack Daly, president of the Connecticut Police Chiefs Association. Daly appointed the sub-committee in August.
According to the report, the first call to police was at 9:35 a.m; the first officer arrived two minutes and 41 seconds after the first radio broadcast of a shooting.
The elapsed time between the first police officer's arrival and police entry to the school was just under six minutes.
The report said officers were delayed in entering the school because they faced what they considered "exterior threats" of a person running outside the school building. The person was detained and later identified as a parent.
"Officers are trained to prepare for more than one threat or aggressor," the report said.
The Newtown Police Department followed their policy on "active shooter incidents" by confronting the shooter as quickly as possible, according to the report.
"History teaches that the typical active shooter only stops when confronted; as a result the quicker the confrontation by police, the better," the report said.
Lanza, who had been a student at the school years earlier, fired more than 150 shots from a .223-caliber Bushmaster rifle before turning a 10mm Glock pistol on himself, according to police.
"Newtown officers were on scene a total of 1 minute and 10 seconds before the shooter committed suicide," the report said.
The Newtown shooting is the second-deadliest school shooting in U.S. history, behind only the 2007 shooting at Virginia Tech that left 32 people dead.
After the 1999 Columbine School shooting in Colorado, where two students shot 13 people to death before killing themselves, the law enforcement practice of confronting a shooter as quickly as possible replaced a "contain and wait" policy.
According to the report, the Newtown Police Department adopted a quick-engagement policy in April 2003 "in keeping with current trend in police training."