If I'm reading the story right they were not aware that the suspect was armed until he pulled the gun so it makes sense that they would try non-lethal force first. I don't know enough about police work to know if a mistake was made on either officer's part but it sounds like he followed procedure. Criticizing him for using non-lethal measure first doesn't seem to be called for.
Which is why, with 2 of them there, they should have been prepared to escalate with the first officer using non-lethal force.
After backup arrives, and not until then, the officer should give a clear warning that “Due to the frequent shooting of police officers in traffic stops deadly force may result from any misbehavior by the suspect”. He should only try to physically approach or handle the suspect when his backup is zeroed in on the target.
If the suspect is cooperative and the violation is minor, the officer should offer an apology and explanation that since many officers have been shot, policy dictates that they must proceed with great caution.