Gatrell has also been charged with arson.
Police say Gatrell did know the victims, but did not elaborate on how.
The bodies of Palmer and Dowdie were found in a burned truck on December 12.
The vehicle had been deserted along a stretch of Wilbern Road in Sweet Home.
Pulaski County authorities haven't said yet what led up to the deaths of the two victims.
Authorities also say at least one more arrest is possible.