A man fatally shot Wednesday night in Richardson was killed by a friend he had been trying to help, according to the victim's mother.
Rene Gamez died at his apartment complex, allegedly shot by Brandon McCall.
Police said McCall then killed Richardson SWAT Officer David Sherrard as he responded to the disturbance call.
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Gamez's mother, Judy Loera, tells NBC 5 her son was generous, hard-working and always willing to help.
She said her son gave McCall a place to stay Tuesday night.
Thursday, she recalled a conversation she had with her son about his gesture.
"My son asked me, he said, 'Hey, Brandon's going to spend the night. I don't want him out in the cold,' and I was like, 'Oh, OK.' So I gave Brandon a pillow and a blanket," Loera said.
She says she never imagined Gamez's good deed would end with him dead.
"I don't know how to accept it now. I'm hurt, and I'm lost and I want to know answers why," she said.
Loera said she has no idea what started the argument between Gamez and McCall.
A relative of McCall told NBC 5 that he lived with the relative for a few years but moved out two years ago and hasn't had a stable home since.
Despite his past, the relative said he never thought McCall would be capable of killing anyone.
McCall is charged with capital murder.
Last August, Dallas police say a family member called 911, saying McCall was threatening to jump off a bridge.
Officers took him to a medical facility for treatment.