A Louisiana state trooper died on Monday after being shot in the head a day earlier during a traffic stop, and the authorities said the man charged in the shooting was being investigated in connection with another fatality.

The state police superintendent, Col. Michael D. Edmonson, described Senior Trooper Steven J. Vincent’s death as “senseless and tragic” and said that the suspected gunman, Kevin D. Daigle, 54, had been charged with first-degree murder.

“Steven was proud to serve as a Louisiana state trooper, and we were proud to count him among our ranks,” Colonel Edmonson said in a statement on the state police Facebook page. “This loss exacts an enormous emotional toll on the State Police family, but we will do what is necessary and proper to honor Steven and support those who knew and loved him.”

Image Senior Trooper Steven J. Vincent Credit... Louisiana State Police, via Associated Press

The state police said Trooper Vincent, 43, was wounded on Sunday afternoon after he stopped to investigate a pickup truck in a ditch in Calcasieu Parish, which borders Texas; the truck had been reported for possible drunken driving. Colonel Edmonson said that the shooting was recorded on video and that Trooper Vincent had offered to help Mr. Daigle, who eventually opened fire with a sawed-off shotgun. The trooper died Monday at a hospital in Lake Charles.