The Conservative MP says he got confirmation of the inquiry from Public Safety Minister Steven Blaney on June 18.
"He provided me his assurance that a full inquiry into the events leading to the tragic death of the three Codiac RCMP officers will be undertaken," Goguen wrote in a recent letter to editor of the Moncton newspaper.
"From this inquiry, best practices in emergency scenarios will be reviewed and strengthened," the letter states.
No timeline is mentioned in the letter.
Goguen could not immediately be reached for comment on Tuesday.
He had declined an interview with Radio-Canada about the shootings on June 18, the same day he says he discussed the matter with Blaney.
Blaney also refused an interview with Radio-Canada.
Employment and Social Development Canada previously confirmed it is conducting an investigation into the shootings. It is unclear if or how that investigation is related to the inquiry Goguen refers to.
On June 4, three RCMP officers were shot and killed by a heavily armed gunman:- Const. Douglas James Larche, 40, from Saint John.
- Const. Dave Joseph Ross, 32, from Victoriaville, Que.
- Const. Fabrice Georges Gevaudan, 45, originally from Boulogne-Billancourt, France.
Constables Éric Stéphane J. Dubois and Marie Darlene Goguen were also wounded in the attack in the southeastern New Brunswick city.
Justin Bourque, 24, of Moncton, is charged with three counts of first-degree murder and two counts of attempted murder in connection with the shootings. He is scheduled to make his next court appearance on July 3.
Goguen's comments come on the heels of calls for an inquiry.
Earlier this month, retired RCMP officer Terry Mckee, who supervised two of the three officers who were killed, told CBC News there should be an external inquiry.
The RCMP has said its investigation into the shootings is ongoing and "may take a while to complete," but it will be "thorough."
An inquiry was held following the shooting deaths of four RCMP constables in the northern Alberta town of Mayerthorpe on March 3, 2005.
The officers were guarding a marijuana grow-op and cache of stolen car parts they had found inside a Quonset hut when the owner of the farm returned and began firing on them with a high-powered hunting rifle. The gunman, James Roszko, later killed himself.
Rob Creasser, the spokesman for the Mounted Police Professional Association of Canada, has said Moncton officers did not have ready access to the ballistic vests or high-powered rifles recommended by that inquiry.
RCMP Commissioner Bob Paulson has said his members have access to the tools they need.