"This is an bad day for Weymouth and for Massachusetts, " District Attorney Michael W. Morrissey said in a statement. A suspect, identified as Emanuel Lopes, was in custody and was expected to be arraigned on two counts of homicide Monday.
Fox Newsreports that Lopes was fleeing on foot when Chesna drew his gun and ordered Lopes to stop. Instead of stopping, Lopes allegedly bashed Chesna in the head with a stone, stole his firearm, and shot Chesna in the head and chest with his own gun, prosecutors allege.
Sources say Lopes uses a different name on Facebook and told officers at the time of his October arrest that he was homeless.
Weymouth Police said Lopes was selling cocaine to a minor and resisted arrest when he was arrested in 2017.
Police then apprehended Lopes and took him to South Shore Hospital for treatment of his wounds, which are not life-threatening.
Neighbors say the suspect had been driving erratically as officers tried to pull him over.
Weymouth police Chief Richard C. Grimes, who hired Chesna, praised his attitude toward his work at a somber news conference at the Weymouth police station Sunday.
Chesna has been remembered by his colleagues as a "great family man and officer".
He was married and had two children, 4 and 9, Grimes said. "I would see him in the morning come in from the street". During that time he allegedly fired Chesna's gun three times at the officers.
Chesna was taken to South Shore Hospital, where he was pronounced dead. Chesna was from Weymouth and graduated in 1994 from Weymouth High School.