BRENTWOOD — A former Derry woman indicted on arson charges is accused of setting three fires inside her own condominium complex because she wanted to frame a neighbor who had fired off a gun inside their building three months earlier, according to a police affidavit unsealed in superior court.

Cheryl Wheaton, 56, formerly 4 Pembroke Drive, admitted to Derry police that she set the fires inside her building at Hillside Estates in hopes that her neighbor would be blamed and kicked out of the complex, police said.

Wheaton, who at first denied any involvement with setting the fires, later told police she sleepwalks and took an “extra” dose of sleeping pills before setting one of the blazes, the affidavit says.

While talking about her sleepwalking with police, Wheaton said, “that it was always on her mind to get certain people from the building to leave,” wrote Derry police Detective Scott Tompkins.

“One of these thoughts was that what if there was a fire and they (her neighbors) were home,” then they would be blamed for the arsons, Tompkins wrote.

Wheaton, now living in Salem, Mass., was indicted last month on three counts of arson in Rockingham County Superior Court.

Each charge is punishable by up to 7½ to 15 years in state prison. No trial date has been set.

Derry police investigated the gun incident on April 27.

Witnesses told police there was a confrontation between three people living in the building and two people who arrived in a white Ford Explorer. Police believe one shot was fired during the incident and the bullet got lodged in a lobby wall.

The affidavit gives the first detailed account of the Derry police investigation that led to Wheaton’s arrest in November.

Derry Fire Inspector Philip LaValley concluded that at least two of the blazes set showed a similar pattern, according to the affidavit.

On the night of July 21 at 11:32 p.m., fire investigators found that someone stuffed a flier from a Big Lots store under a door to one of the empty units and then lit it on fire. Wheaton lived in the unit next door.

“A small section on the bottom of the door had been burnt as well as the surrounding ground area,” Tompkins wrote.

Paper towels and an accelerant were used to set another fire on Oct. 30.

Investigators found pieces of paper had been ignited in several places around a first-floor laundry room sometime before police and fire crews responded at 12:38 a.m.

After that fire, police recovered samples of burnt paper towels and a partially burnt can of Kano Aero Kroil, an industrial lubricant rarely distributed in New Hampshire, the affidavit says.

Wheaton’s husband, who was interviewed by police, acknowledged having a can of the lubricant but could not find it when police asked him to locate it, the affidavit says.

Fire officials also investigated a small fire in the building on May 22. A wooden box containing magazines and fliers were burnt in the front foyer of Wheaton’s apartment building, the affidavit said. Fire investigators were unable to pinpoint the cause of that fire, and Wheaton denied setting that blaze. She was not charged in the incident.

Before Wheaton was arrested, neighbors told police they saw her in a hallway immediately after the Oct. 30 fire with her dog on the leash. Wheaton claimed she was walking her dog during a snowstorm, but she was not wearing a coat and she did not show any sign of being wet, police said.