I was an EMT-B back in the day, and one of the first things they drilled into our heads during training was to never run at a scene. There were numerous reasons, all very practical, including:

• If you run, you're more likely to trip and fall, or drop something, or bump into another first responder also running around, which of course can get you hurt, and endangers the patient due to delaying their care and transport if you do get hurt
• You really should never be so rushed or panicked to even want to run. Staying controlled and calm is important to make sure you can provide thorough care, versus frantic and scatterbrained
• If you are running at a scene, bystanders and even worse loved ones of the patient, are going to freak out more because they'll think "oh shit it must be really bad if the EMT is running". Which then gets them spun up and in your way, a lot of the time.

But all of that aside, if these guys really did interrupt responding to an ALS call, they are awful and deserve to be fired ASAP.