Perhaps they were set to meet up after? There were witnesses to Tippitt’s killing.
There are several witnesses to JD Tippitt’s murder.
This is the only believable witness https://youtu.be/zTjq7jz8b5g
The other “witnesses” are obviously lying.
Combine that with the gas station attendant (who corroborated Clemson’s observations) and you have proof. The gas station attendant subsequently changed his tune after he was shot (but survived).