A 21-year-old Navy man was killed in cold blood Saturday after stopping to help someone who appeared to be a “stranded motorist” on a San Diego interstate.

Brandon Acuna, 21, was taken into custody and arrested on suspicion of first-degree murder and burglary, confirmed San Diego police Lt. Anthony Dupree, who also said others may have been involved in the Saturday shooting, reported the San Diego Tribune.

The victim, Curtis Adams, was driving with his girlfriend around 2:20 a.m. when they spotted a man standing next to a white vehicle on the shoulder of the freeway. The couple pulled over and Adams got out of the car.

Adams was immediately shot while shooter got back in his vehicle and fled.

Acuna was also named as a suspect in a second shooting that happened just 10 minutes before Adams was killed. In this incident, said police, a man was shot for trying to stop a suspect from breaking into his vehicle.

Detectives are working to determine who else was involved in that incident, and everyone’s level of involvement, including Acuna’s.