BRATTLEBORO -- Brattleboro Police Sgt. Mark Carignan was "legally justified in the use of deadly force" when he shot and killed a man during execution of a search warrant April 4, the Vermont attorney general's office has ruled.

Attorney General William Sorrell on Thursday announced his findings after a nearly three-month investigation into the death of 35-year-old Michael Santiago at America's Best Inn in Brattleboro.

Though no firearms were found at the scene, police had reason to believe that Santiago might have had weapons, investigators concluded. And Santiago's actions, including concealment of his right hand in spite of warnings from police, led officers to believe they could be shot, officials said.

"Under the facts of this case, the attorney general's office concluded that Sgt. Carignan was reasonable in his belief that he and the other officers executing the search warrant were in imminent danger of death or serious bodily injury when he fired at Michael Santiago," the attorney general's statement says.

"Given what reasonably appeared to be a serious threat to his life and to the life of the other officers, Sgt. Carignan's response of using deadly force was reasonable and justified," the report says. "The Bennington County State's Attorney's Office has completed a separate and independent review of the investigation and has reached the same conclusion."

Bennington County had taken the investigation at the request of Windham County State's Attorney Tracy Shriver, who had stepped aside from the matter due to her office's close relationship with Brattleboro police.

In the early morning hours of April 4, police were executing a search warrant on Room 301 at America's Best Inn on Putney Road. It was part of an ongoing drug probe.

Santiago and Amanda Piermarini were staying in the room.

"The search warrant authorized the officers to search for and seize both Santiago, for suspected violations of his conditions of release in two pending prosecutions, and heroin," the attorney general said.

Officers were prepared for the possibility of an armed confrontation, the document states.

"Prior to the execution of the search warrant, the officers received information from law enforcement in a neighboring jurisdiction indicating that Piermarini and Santiago may have recently acquired several firearms," according to the report. "Furthermore, several of the officers, including Carignan, were aware of a previous incident during which Santiago possessed a knife and resisted arrest."

Police unlocked the door with "a lock override device" provided by the inn. But they could not fully open the door because an internal lock chain was engaged.

"When the officers opened the door as much as possible, Sgt. Carignan observed Santiago move towards a dresser located in the back of the room. At this point, Carignan shouted, 'police search warrant,'" the attorney general said. "In response, Santiago slammed the door shut. The officers reopened the door with the assistance of a ram."

When the door was open, the report says, "Carignan repeatedly directed Santiago to show the officers his hands. Santiago ignored these commands and kept his right hand concealed behind his back. Several of the officers stated it appeared as though Santiago was holding or manipulating something."

"Carignan then warned Santiago that, if he did not comply with the instructions to show the officers his hands, he may be shot," the attorney general said. "In response, Santiago advanced towards the officers while moving his right shoulder and arm -- an officer described the motion as being consistent with drawing a firearm. When Santiago did so, Carignan shot him twice with his shotgun."

Carignan summoned medical help, the report says, but Santiago died from his injuries at the scene.

Piermarini was taken into custody without incident. Police found 10 bags -- which is equal to one bundle -- of heroin inside Santiago's boxer shorts, and there were several bundles of heroin and more than $2,000 cash inside a dresser, the report says.

But there were no firearms found.

Asked how prominently that fact figured into the investigation, Assistant Attorney General John Treadwell reiterated that the officers believed Santiago and Piermarini had purchased firearms. Treadwell also pointed to Santiago's movements during the encounter with police.

The notion that Santiago was armed "turned out to be mistaken, but that does not mean it was unreasonable," Treadwell said.

The attorney general's statement added this: "The legal standard for the use of deadly force is whether the officer reasonably believed that he or a third party was in imminent danger of death or serious bodily injury, and that deadly force was necessary to respond to that threat."

Carignan, a 12-year veteran of the Brattleboro department, was placed on administrative leave after the shooting. He returned to active duty after about six weeks.

Santiago had a history of run-ins with the law. He reportedly had a heroin conviction in Windsor County and a possession charge pending in Chittenden County. At the time of the shooting, he was due in Windham Superior Court Criminal Division on theft and credit-card fraud charges, and Brattleboro police in November 2013 claimed Santiago had attempted to flee and assaulted an officer during an investigation.

Thursday's report says Piermarini confirmed the facts of the America's Best incident during her interview with law enforcement. Piermarini has not been charged in Windham County, and it is unclear whether she will face prosecution.

The attorney general's office said the investigation included interviews with the officers who executed the search warrant and other people who had been staying at the inn. Also, the Vermont State Police Crime Scene Search Team was involved, and the State Police "collected various photographs, reports from the officers, the rescue personnel and the medical examiner as well as other miscellaneous documentation."

The Reformer has requested the official Vermont State Police investigation report. But officials have several days to fulfill that request, and the document may be redacted to protect confidential sources and/or prevent the release of sensitive information.

Mike Faher can be reached at mfaher@reformer.com or 802-254-2311, ext. 275.