An active duty sailor in the Navy met a tragic end when he pulled over to help a stranded motorist.

According to the San Diego Union-Tribune, Curtis Adams was with his girlfriend when the couple spotted a man standing next to a white vehicle on the shoulder of the highway. The couple pulled over to help.

As soon as the 21-year-old got out his car, the man he'd stopped to help shot him. The shooter returned to his vehicle and sped away as Adams' girlfriend called the police. 

Soon after the shooting, Brandon Acuna was taken into custody and arrested on suspicion of first-degree murder and burglary after police questioned him. Police have not yet revealed whether Acuna acted alone in killing Adams.

Police say the suspect is believed to have been behind another shooting that took place only 10 minutes before Adams was murdered, NBC San Diego reports. The first shooting occurred during a carjacking. Authorities believe the victim tried to stop Acuna and at least one other accomplice from stealing his car and was shot.

Acuna has a criminal history dating back to 2015 when he was just 18 years old. 

Detectives are currently working to determine Acuna's motive.

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