Demetrius Lynell Simpson, 35, is accused of murder, possessing a bomb, stealing a gun, and beating up an old roommate.
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Court documents say it began on April 6 when he walked into the Academy Sports and Outdoors store at 21650 Kuykendahl Road.
While testing out a 9mm handgun, records say he walked away with it and ran from employees chasing him.
Within an hour, he allegedly sold the gun to a pawn shop for $300.
A month later, on May 4, he is accused of beating up a former roommate he spotted at the Metro Transit Center in Greenspoint. The victim says he requires facial surgery for a broken nose.
And on June 28, Harris County sheriff's investigators were called to the fatality scene at a business center located at 14647 Walters Road.
They say a 65-year-old homeless veteran named Louis Roberson was found shot in the business center parking lot where he was known to live off TC Jester and FM 1960.
"He was found by a friend who meets with him every morning to have breakfast and coffee. The male came here, he discovered him here where he sleeps at," Sgt. Greg Pinkins said.
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The suspect, police say, lived just a mile away where inside his home, court records say they found "a functional pipe bomb in his room."
Simpson is now behind bars facing four charges, including murder.
Sources close to the investigation say Roberson was a disabled veteran experiencing homelessness.
The suspect has a court date for Friday, where bond for the murder charge is expected to be set.
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