Alan Hruby, 19, takes responsibility, according to police, after authorities find cracks in his timeline and whereabouts

A housekeeper’s shocking Monday morning discovery of three bodies – a small-town Oklahoma newspaper publisher, his wife and their teenage daughter, all dead in their upper middle-class home – led authorities to seek out the fourth member of the family, 19-year-old Alan Hruby.

The housekeeper’s daughter reached him by cell first and summoned him to the house. When he accompanied police in Duncan, Oklahoma, to the station to hear about the early stage of their investigation, “he was obviously very distressed,” Police Chief Danny Ford tells PEOPLE. “He became very upset. We had him with a chaplain for, I don’t know, a good long while.”

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But during the conversation about when Hruby had last seen the victims and where he’d been, “some of the timelines and things that he was giving us were not matching up with information that we had,” says the chief.

An investigator remembered that Hruby, a political science major at the University of Oklahoma that is 75 miles away, was suspected in a pending stolen-check complaint – reason enough to arrest him that night and hold him for further questioning.

Then late Tuesday, says Ford, “He confessed and gave a pretty good description of what went down,” taking responsibility for the murders of his father, John Hruby, 50, his mother, Joy, 48, better known locally as “Tinker,” and his sister, Katherine, 17.

“It’s a prominent family, well-known and extremely well-liked. Grew up here, went to school here. John was a graduate of Duncan High School,” says Ford. “The son graduated from Duncan; the daughter was a junior, I believe. Everybody knew the Hrubys. Everybody.”

Stephens County District Attorney said in a press conference Wednesday the murders occurred last Thursday, when Alan shot the victims with a Walther 9mm pistol that had been reported stolen earlier that day by his father. Hick said Alan confessed to owing $3,000 to a loan shark, and felt the murders would generate an inheritance so he could pay off his debt, reported NewsOK.com.

After the shootings, Alan disposed of the gun and a DVR disc from the home’s security system by tossing both in a lake, he said.

The prosecutor said the death penalty for the murder charges filed Wednesday would “seriously be considered.”

According to the Tulsa World, Alan had been charged in 2013 with credit card fraud after his father discovered that he, then traveling in Europe, had applied for credit cards using his grandmother’s name and rang up nearly $5,000 in charges while overseas.

Because Alan was on probation in connection with that offense, his statement that he’d spent the weekend prior to the discovery of the murders out-of-state – allegedly in Dallas, where he told police he stayed at the Ritz-Carlton and attended an Oklahoma-Texas football game – was an apparent parole violation that further led to his arrest, the chief says.

But otherwise, Ford tells PEOPLE he knew of nothing to indicate that Alan was a problem kid.

Following the murders, “we’ve had people out in the community that have given us information that he was giving Mom and Dad some trouble, but we’ve not had much contact with him that I’m aware of,” he says. “The credit card and the checks was the first I’ve heard of it.”

“There’s people that are shocked. They’re having a hard time grasping that this would happen – in the community, first, and second, to this family.”

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