From Prince William County:
Calling is still the best way to contact 911 in an emergency, but in certain situations, a text might be better. The Prince William County Office of Public Safety Communications can now accept text-to-911 emergency messages from AT&T, Sprint, T-Mobile and Verizon Wireless customers who find themselves needing assistance in Prince William County and the cities of Manassas and Manassas Park. The service should only be used when someone has a physical disability or special need where calling is not possible or when speaking out loud would put the caller in danger.