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(CNN) —  

As police hunted the man they believe killed a prominent Houston doctor, their suspect in the July 20 shooting seemed to have led a double life.

Joseph Pappas, 62, did ordinary things, like mowing his own lawn, a neighbor reported. But he also handed a courier paperwork to transfer his home deed and told the beneficiary he planned to kill himself, she told a newspaper.

Pappas realized that plan Friday morning, when he took his own life as two police officers confronted him in a southwest Houston neighborhood, Police Chief Art Acevedo said. He was not far from his home and was wearing a bullet-proof vest, the chief said.

Investigators this week had become more convinced that Pappas “painstakingly planned” the bizarre daylight execution of Dr. Mark Hausknecht – carried out as both men rode bicycles – possibly as revenge for his mother’s death 20 years ago under the doctor’s care, Acevedo told CNN Thursday.

Further, the notion that Pappas, a trained marksman who worked for 30 years as a Texas constable, apparently hid in plain sight while putting his affairs in order added intrigue to a murder that already had put the nation’s fourth most populous city on edge.

Thursday night, after someone reported seeing a man riding a bike near Pappas’ home, SWAT teams and officers entered the residence, Houston Police Executive Assistant Chief Matt Slinkard said.

An officer reported that a light was on inside the home and a back gate was open, but Pappas wasn’t there, Slinkard said.

Police had warned that Pappas could be armed and dangerous, and – thanks to his law enforcement background – might have access to police radio and tactical channels to monitor the dragnet police had cast to catch him, Acevedo said.

In the end, an employee of the Houston parks board called authorities Friday to say he’d seen Pappas – and he found a wallet with the suspect’s ID that Pappas had apparently left on the ground, Acevedo said. The employee had been checking the area for graffiti.

Anxious to transfer deed

Even as the manhunt dragged on earlier Friday, Pappas’ activities since Hausknecht’s killing were becoming more clear.

The day before the shooting, Pappas, who also worked as a real estate agent, transferred the deed to his southwest Houston home to a woman who lives in Ohio. And he appeared to be in a rush to make that happen.

A courier who went to Pappas’ home three days after the killing to fetch deed paperwork and ferry it to a courthouse said Pappas acted strangely.

“He was very nervous,” said Joe Donalson of Legal Express Texas.

Pappas cracked the door and peeked out, then opened it wider.

He was “looking up and down the street, to see if anybody else was there,” Donalson said. “And then he passed me the envelope.”

Pappas called Donalson three times that day to make sure the documents were filed, the courier said. He said the transaction seemed odd to him, but his line of work demands confidentiality, so he didn’t ask many questions.

The document transferred the home deed to a woman from Ohio on July 19, but didn’t indicate whether the three-bedroom, 2,100-square foot ranch house was sold. Donalson said he couldn’t pick up the paperwork on July 19, and Pappas called him again on July 23 to get it.

Janette Spencer of Painesville, Ohio, said she received notification in the mail on July 23 that the home had been deeded to her, the News-Herald in Ohio reported. CNN was unable to contact her Thursday.

“I called him on the 24th, and he said he had a terminal illness, and that’s why he deeded (me) the house,” Spencer told the paper. She said she’s known Pappas for about 25 years.

One of Spencer’s daughters was supposed to meet Pappas on July 30, when she visited Houston. However, Pappas texted Spencer that day to tell her he was committing suicide and gave her instructions for how to secure the house.

“Sorry for handling things this way,” the text said, according to the paper. “House and property is now yours. Please make best use of it for you and (your daughter).”

Spencer told the paper they tried to contact Pappas after receiving that text, but calls went straight to voice mail. They then called police.

A delinquent property tax statement from Harris County, Texas, shows Pappas owed $4,409 in back taxes, penalties and interest on the property. The notice said that if the amount wasn’t paid in August, the property would be subject to a lien.

Donalson said he called police after watching a news conference in which Acevedo named Pappas as the suspect in Hausknecht’s killing.

20-year grudge?

Police had searched Pappas’ home earlier this week after getting a tip from a neighbor.

“We found plenty of evidence that shows an extreme interest by (Pappas) in the doctor,” Acevedo told CNN on Thursday.

“If you think about his fascination with the doctor and the fact that he ends up killing this man in cold blood, the only thing we can think of is the connection between his mother dying over 20 years ago during surgery,” Acevedo said. “Until we talk to him, we can’t say definitively that that’s the motivation behind this killing, but there’s nothing else that would explain it.”

Investigators had discovered “an extensive intelligence file” at Pappas’ home, Acevedo added Friday. Though it wasn’t “a hit list,” one sheet contained “a couple dozen” names of other doctors and employees from the same Texas Medical Center facility where Hausknecht worked, the chief said.

The information was shared with Texas Medical Center, Acevedo said. No one with the facility wanted to comment Friday.

Authorities issued an arrest warrant for Pappas after the first search of his home.

Errol Francis, who lived near Pappas for many years, told CNN that the suspect was “sort of a lonely person.”

Francis said he would see Pappas only when he mowed the lawn, including on Sunday. He was always a quiet guy, Francis said.

Pappas’ parents had lived at the home, Francis said, and when the mother died in 1997, he didn’t notice any change in the son’s behavior.

Suspect’s number is linked to a firearms website

Pappas had worked for three decades as a constable, according to Texas Commission on Law Enforcement records. He worked for Harris County as a peace officer and a reserve officer from May 1983 to July 2013. He also took law enforcement classes through last August, documents indicate.

Also, Pappas’ phone number is linked to recent listings on a firearms auction website for several guns, ammunition, tactical vests and ballistic plates for car doors. The posts, from a user in Houston, apparently went online days after the shooting.

It is unclear whether any of the firearms listed online were used in the Hausknecht shooting. A Houston police spokesman declined to comment on the ads.

Pappas and Hausknecht were on their bicycles on July 20 when, police said, the suspect rode past the doctor before turning around and fatally shooting him. Surveillance images showed the suspected gunman just behind Hausknecht as both headed north on a highly trafficked street in Houston’s Medical Center district during rush hour, police said.

The prominent surgeon and former cardiologist for President George H.W. Bush was found near a construction site where hundreds of workers were present, but the equipment was loud enough to mask the sounds of gunfire.

CNN had tried unsuccessfully to reach Pappas as recently as Wednesday at the phone number listed for his real estate company.

Doctor remembered as gentle and caring

Hausknecht and his wife, Georgia Hsieh, lived in an upscale neighborhood not far from the Texas Medical Center in southwest Houston. In addition to his wife, a retired emergency room physician, Hausknecht is survived by two adult sons, Matthew and Paul.

Hausknecht’s family released a statement Thursday thanking Houston police and others who helped identify a suspect, and asking the public to focus on Pappas’ photo and contact police if they know where he is.

Friends and colleagues remembered the doctor as a quiet, generous and kind person.

“He was very gentle, he was very caring, he offered a lot to people in need,” Dr. Neal Kleiman said. “That was his personality, and that was his family’s personality, too.”

CORRECTION: This story has been updated to correct the time reference to the latest police activity at Pappas’ home.

CNN’s Ed Lavandera, Majlie de Puy Kamp, Michelle Krupa, Jamiel Lynch, Darran Simon and Pierre Meilhan contributed to this report.