With 2 officers, one of them should have had his gun drawn.
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.