UPDATED | July 9, 2015 10:52 AM

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ARLINGTON (CBSDFW.COM) – What was initially believed to have been an incident that left a suspected home intruder dead, and also resulted in the fatal heart attack of the gun wielding homeowner, is getting complicated.

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Now, Arlington police say homeowner David Stephenson may have known the man he shot and killed in his garage Wednesday night.

Police say what happened at the home, in the 3400 block of Spring Meadows Drive, does not appear to be random and they are looking at the possibility of other “high risk behavior” that could have been occurring at the time of the shooting.

Investigators spent more than eight hours at the scene – conducting interviews and collecting evidence.

Before it was known that the shooter and shooting victim knew each other, police said Stephenson heard a noise in his garage late Wednesday night and called 911. When officers arrived at the house they found suspect Destrey Tinner shot in the shoulder. The 24-year-old was rushed to a nearby hospital, but later died.

Then, while speaking to investigators about the shooting, Stephenson began having trouble breathing and appeared to be having a heart attack. The 54-year-old homeowner was rushed to Medical Center of Arlington but passed away.

Stephenson’s wife, Marge, was home when the shooting happened. After her husband died she said, “He was a great man. He would do anything for anyone and for this to happen is not right.”

Neighbors said they knew Stephenson had some health problems. Sylvester McCaleb lives next door. “He’s had heart trouble for quiet some time. I guess the excitement was too much for him… real good neighbor [who] really will be missed.”

Sylvester’s wife, Ruth, said, “Oh my God. I’m so hurt. I’m so hurt for his wife and his children ’cause they’re really close.”

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The deceased suspect, Destrey Tinner, has a criminal past. Tinner, who is originally from Amarillo, previously faced charges in a Tarrant County assault family violence case.

Stephenson also has a criminal history. He was arrested in 2001 for possession of marijuana. He was placed on a 6-month probation deferred adjudication and the case was dismissed a year later.

The McCaleb’s said they had a running car stolen from their driveway several months ago, but that for the most part their neighborhood is very quiet.

Destrey Tinner’s mother told CBS11 Thursday afternoon, she believes the incident that left her son and another man dead, was possibly a case of mistaken identity.

Jacqueline Irving said she and her children knew David Stephenson as “Pops.” The two families grew up down the street from one another, and Stephenson and the kids still spent time together.

“It’s very strange for Pops to shoot my son,” she said. “He would never in his life hurt him.”

Arlington Police said late Thursday they were still investigating what led to Stephenson shooting Tinner, but said they were confident it was not a burglary or home invasion. Police recovered two guns at the scene, but could not say yet who they belonged to or how many shots were fired.

Police would not go into detail about information from neighbors that there may have been some type of “at-risk” behavior at the house. Irving said her son did not have a gun, but that he and Stephenson often smoked marijuana together at the home where the incident happened.

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