NORTH LITTLE ROCK, Ark. — It was appropriate that National Guard medic Sgt. Russell Collier was unarmed and tending to a fallen comrade when he was killed in Iraq, his sister said.

“He died doing what he loved and if he had to die, he would have wanted it this way,” said Carolyn Pfaus, 39, of Conway, talking about an older brother she described as protective.

While on patrol near Baghdad on Sunday, Collier, 48, became the 14th Arkansan and the 19th member of the 39th Infantry Brigade killed in combat in Iraq since the war began, Capt. Kristine Munn said Tuesday.

When Sgt. Christopher Potts, a member of Collier’s brigade from Tiverton, R.I., was hit by small-arms fire, Collier handed his rifle to another soldier and ran to Potts’ side, with only his medic’s bag in tow, Pfaus said. He was killed before he got to...