End of watch: Yarmouth Police Department Sgt. Sean Gannon killed 3 years ago Share Updated: 6:19 AM EDT Apr 12, 2021 Sgt. Gannon Share Updated: 6:19 AM EDT Apr 12, 2021 Monday marks three years since a Yarmouth police officer was killed in the line of duty.Sgt. Sean Gannon was shot and killed while serving a search warrant on April 12, 2018. Gannon s K-9 partner Nero was also shot and injured that day. Gannon s widow, Dara, has previously asked that people remember her husband with an act of kindness.Gannon was a New Bedford native and a graduate of Bishop Stang High School in Dartmouth and Westfield State University.