The home's owner, Monserrate Shirley; her boyfriend, Mark Leonard; and his brother, Bob Leonard, were arrested Friday and charged with murder, arson and other counts in the Nov. 10 blast that killed two people.

Shirley, 47, was facing mounting financial woes, including $63,000 in credit card debt and a growing threat she might lose her home amid bankruptcy proceedings, court documents say. And a friend of Mark Leonard's told investigators Leonard said he had "lost a ton of money" — about $10,000 — at a casino some three weeks before the explosion.

Investigators believe the trio had actually tried but failed to blow up Shirley's home the weekend before the successful timed explosion, according to Marion County Prosecutor Terry Curry. The fiery blast destroyed five homes, including Shirley's, and caused widespread damage to dozens of others in the Richmond Hill subdivision in the far south side of the city.

Curry called the explosion a "thoroughly senseless act" that killed Shirley's next-door neighbors. He said the victims, John Dion Longworth, a 34-year-old electronics expert, and his 36-year-old wife, second-grade teacher Jennifer Longworth, were "in the prime of their lives."

Randall Cable, the attorney for Shirley and Mark Leonard, said he was stunned by their arrest.

"I'm just as surprised as everyone else that they've made an arrest. My clients have consistently indicated their innocence," he said.

Shirley and the Leonard brothers face two counts of murder as well as 33 counts of arson — one count for each of the homes damaged so badly that officials have ordered their demolition.

Curry said his office would review whether to pursue the death penalty or life in prison without parole against the three, who are scheduled to appear in court Monday.

Shirley and Mark Leonard, 43, also face two counts of conspiracy to commit arson, while Bob Leonard, 54, faces a single count. Curry said the conspiracy charges stem from the failed explosion.

He said investigators determined that Shirley's home filled up with gas after a gas fireplace valve and a gas line regulator were removed. A microwave, apparently set to start on a timer, sparked the explosion, he said.

On Friday, workers using heavy equipment were removing debris from razed homes in the neighborhood.

Doug Aldridge, the head of the Richmond Hill's crime watch group, said after a neighborhood meeting that the allegations are "more than we anticipated."

"Sometimes money makes people do stupid stuff," Aldridge said.

Investigators found that in December 2011, Shirley's home insurance policy for personal property was increased to $304,000 — an amount that was in addition to the coverage for the home itself, according to court documents.

A probable cause affidavit says Shirley filed for bankruptcy this year but stopped making her court-arranged payments and failed to appear at a July bankruptcy hearing. The home's original loan was for $116,000 and a second mortgage was taken out on the home for $65,000, the affidavit says.

A friend of Mark Leonard's also told investigators that Leonard would surf online dating sites "and located older, heavier women, wine and dine them," then borrowed money and never paid them back, according to the affidavit.

The friend said Shirley was aware of the scheming "and was OK with it so long as he did not sleep with the women," the affidavit says.

Leonard has a criminal record that includes stalking and intimidation and convictions on dealing and possessing cocaine, according to prison records.

Two men, one fitting Bob Leonard's description, were seen at Shirley's home the day of the explosion, and Curry indicated investigators believe that's when the gas line and valve were tampered with. He said authorities are still trying to determine the second man's identity.

Curry said that the day before the blast, the brothers asked an employee of local gas utility Citizens Energy several questions, "including the differences between propane and natural gas, the role of a regulator in a house and controlling the flow of natural gas and how much gas it would require to fill a house."

Curry said Shirley and her boyfriend had followed the same pattern two weekends in a row, visiting a southern Indiana casino, dropping off Shirley's daughter with a baby sitter and boarding the family's cat.

An affidavit says that when a friend of Mark Leonard's called him Nov. 2, eight days before the successful blast, Leonard told the friend "the house blew up" and that he and Shirley were staying in an efficiency apartment.

In another call that day, Leonard told his friend he had been surfing Craigslist "looking for a Ferrari to buy" and explained that he could afford the luxury car because Shirley had jewelry insurance and "they expect to get $300,000 and he would get $100,000" in the insurance payout, according to the affidavit.

It's not clear whether investigators think Leonard believed the first explosion attempt had succeeded. Curry's spokeswoman, Brienne Delaney, said the office could not comment beyond what was in the court documents.

The day after the explosion, Bob Leonard allegedly called his son and asked him to retrieve from a white van items he said he had salvaged from Shirley's home after the blast.