A 33-year-old man has been arrested in connection with the December 2016 fatal shooting of an Arlington mom who was trying to sell jewelry to buy Christmas presents for her 6-year-old daughter, police say.

Arlington detectives, working with a U.S. Marshals task force, arrested Mario Hernan Lopez Gamez on Saturday.

Investigators said 33-year-old April Vancleave listed some jewelry for sale online in December 2016. Then, she and her husband agreed to meet the potential buyers inside the Target store on West Arbrook Boulevard, thinking they would be safe in a busy public place.

But when Vancleave and her husband came to meet the potential buyers at Target, they didn't show. Detectives believe they followed the couple home, instead, and when Vancleave's husband dropped her off and left for work, police said two men pulled up, stole her purse and shot her once, killing her. [[408861085,C]]

"I believe heavily in karma. They killed someone in cold blood and they're going to get what's coming to them," said Vancleave's stepsister, Margie Morton Aguirre.

Although police made an arrest, Aguirre said there will never be closure for the family.

"It still opens up old wounds. It was senseless. It was tragic. There was no reason for it," Aguirre said.

Lopez's bond was set at $150,000, according to an arrest warrant and affidavit issued for him.

The arrest warrant and affidavit also said a woman from Mansfield helped police connect the dots in the case.

After the murder, police released surveillance video from the Target showing two men that police believed may have been involved in Vancleave's murder.

Documents reveal the woman recognized the two men in the surveillance video. The woman called police and said the men responded to her resale ad.

She claimed she was robbed by them in November, the arrest warrant and affidavit said.

In the documents, police said one of the men in the surveillance video is Lopez. The status and identity of the other man in the video was not immediately known.

NBC 5 Reporter Alice Barr contributed to this report.