The Daily Camera reports the Wheat Ridge-based Animal Law Center filed the lawsuit in Boulder on Thursday on behalf of Brittany Moore and her three daughters.
Representatives for the town and police declined to comment because they hadn't been served with the lawsuit yet.
Officer Jamie Chester has said he fired after Moore's dog bared its teeth and lunged at him last year.
Moore disputes that and says the dog had followed her as she walked over to talk to Chester, who was responding to Moore's 911 call about threatening phone calls.
The district attorney's office declined to prosecute Chester.
(Copyright 2012 by The Associated Press. All Rights Reserved.)