While a TASER may be a better option at times, pepper spray can be a practical choice. The key is to know when the use of pepper spray is appropriate and will be effective.
A recent decision by the U.S. Court of Appeals for the Fourth Circuit, which applies to five states, emphasizes the use of TASERs as tools for protection, not for compelling compliance.
The suspect has advised that if anyone comes near his mother he "will take them out." You also know the sergeant asking for help uses poor tactics and will count heavily on his personal relationship with the suspect.