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DALLAS (CBSDFW.COM) – Three men were arrested in a murder investigation after a separate sex trafficking case led detectives to the suspects.

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Irma Martinez, 49, was sitting in her car Monday night on Greendale Drive waiting to pick up her son, when police say two men approached her, stole her cell phone and shot her before a third man drove them away. Two days later police say all three men were arrested as part of a sex trafficking ring.

Investigators aren’t saying much about the sex trafficking crimes, but John Paul Manuel, 19, Antwan Tovar, 26, and Terrance Brown, 18, were all arrested Wednesday in what detectives say was the getaway car following the Martinez murder.

Investigators also matched a pistol found on the men with spent shell casings found at the murder scene.

Then Thursday night police say Manuel admitted to detectives what roles each of the three men played in the murder of Martinez. According to the arrest affidavit Manuel claims all three saw Martinez and planned to rob her, but it was Tovar who shot the woman twice and took her cell phone, and Brown drove the getaway car. Police say the story matches neighborhood witness accounts, but what they cant understand is why this happened.

“An innocent victim. It sends chills to my spine just even thinking about it. Just sitting there minding your own business, waiting to get your son, 43 and all of a sudden you have somebody walk up to you and shoot you and take your cell phone. I mean it doesn’t make any sense,” says Dallas Deputy Chief Gil Garza.

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CBS11 asked police for more information about that sex trafficking case that led to these arrests. They would only say it involves the three suspects trafficking a female child for prostitution at a hotel.

(©2014 CBS Local Media, a division of CBS Radio Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)

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