ST. LOUIS COUNTY — It's a somber time for a St. Louis County family that experienced a tragic nightmare. It’s because their son was killed, and they still don't know why.

It happened outside of a Walmart in South County last week. Since the shooting, the person responsible for his death has been arrested but police are still trying to figure out why he was shot down.

Alexander Marley was an executive chef less than a mile from where he was killed. Marley’s mother Cynthia Andrews said he was known for helping anyone who needed it and she believes that's what caused him to lose his life.

“We lost him he was trying to do the right thing, but it was to the wrong man,” Andrews said.

Police said that man responsible is 38-year-old Jesse Michael Kelly. They believe he approached Alex for help at a nearby gas station and shortly after he took Alex's life.

And Marley’s father said it’s a pain that he can’t even describe.

"You can’t prepare yourself, you can’t deal with it, you can’t get over it. He killed my son and yet he's not up for a death sentence. This is absolutely insane we need to change the laws," Marley said.

And Alex’s entire family said they won’t stop until his killer pays for their son’s life.

“I’m not going to sleep, Alex’s dad is not going to let this rest, his stepfather, his sister, were not going to let this rest until justice is done,” Andrews said.

Jesse Michael Kelly is being held on a $500,000 cash bond. He's facing multiple felony charges including second-degree murder and armed criminal action.

Police said he’s also being charged with armed robbery after possibly carjacking a teenager earlier that day in the Central West End. And court documents show he was released from prison within the last year after serving time for arson.