SAN FRANCISCO (KRON) — We’re learning more about what happened in the moments leading up to this week’s deadly shooting outside of a San Francisco Walgreens located near Westfield Mall.

Police have arrested a private security guard in connection with the shooting.

KRON4 spoke with the victim’s mother. The victim’s mother says she is still in disbelief. The mother is angry about what she says looks like a security guard’s gross overreaction to a petty crime.

“All I remember thinking is my baby, my baby and I couldn’t do anything but cry out and I asked him, and I asked him if he was sure,” Kevinisha Henderson said.

Henderson can’t stop thinking of the moment she found out her child was gone. Chynna Brown, who preferred the name Banko Paso, was killed Thursday afternoon.

Investigators tell Henderson they believe it started with Paso shoplifting from Walgreens near Market and 4th Street.

It ended with a private security guard allegedly shooting and killing Paso.

Police have arrested the guard, identified as Michael Anthony, and charged him with homicide.

“When they watched the video, there was absolutely no reason for him to do what he did,” Henderson said. “I don’t understand why a Walgreens security guard would have a gun.”

Henderson says she has been speaking with investigators and the district attorney to learn more about her child’s alleged killer.

“I was angry, I was hurt. I wanted to know how old he was, what color he was and where was he from. I wanted to know if it was a hate crime,” she said.

She wonders if Paso’s race, gender or gender identity had something to do with the shooting. Paso identified as a trans man.

“For a while, he struggled with his identity. Lately, he had been experiencing some fear,” Henderson said.

Henderson says police were not able to share the suspect’s statement with her because of the ongoing investigation.

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She says all she can do now is hold on to the memories of her son and see the homicide case through.

“He was just a very, very beautiful person.”

Henderson tells me Paso would want to be remembered for his smile, his joy, and for always being true to himself. The security guard is expected to be arraigned on Monday.