MANSFIELD, Texas -- The family of an 18-year-old man who was killed in parking lot of a Target store begged someone to come forward with information to crack the case.

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Video: Mother Seeks Answers In Teenage Son's Slaying

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The body of Danny Ramsey was found in the parking lot of the Mansfield Target store he worked at off Highway 287 and Debbie Lane on June 9.

"This is my first-born, my baby, and they took him away from me," said Adreana Ramsey, his mother. "They need to come forward. They need to tell that they did this and why."

Ramsey said she was always strict with her son, who had a "contagious" smile.

"He was a momma's boy, 100 percent -- all the way," she said.

She said her son told her on June 8 that he was going to a party.

"He was going to be going with a guy from work to a party, and I asked him not to go to the party," Ramsey said. "I told him, 'Bad stuff happens at parties.' And he said, 'I'll be okay, Momma. I'll be fine.'"

Early the next morning, he was found dead. Police said he was shot twice.

"I should have never let him go," Ramsey said.

Mansfield detectives tracked down the party and interviewed his friends and coworkers, but police are still not clear on what happened after he left the party.

"Now they can't have their son back they at least want closure," Detective Barry Moore said. "That's what we're working toward, is getting that closure for them."

Surveillance video from the Target parking lot showed what may be the gunman's car. Police are still trying to identify who was inside the vehicle.

Investigators said they believe there is at least one witness who holds the key to solving the mystery.

Target is offering a $10,000 reward in the case, and callers can remain anonymous.