Our most immediate association of an assassination committed in a church is that of Archbishop Oscar Romero. Dr. George Tiller, 67, a physician, was killed standing in the foyer of his church; he was serving as an usher, greeting parishioners and visitors. From George Tiller Suspect May Be Charged Monday,

by Joe Rodriguez, Tim Potter and Stan Finger of the Wichita Eagle:

Monday, a 51-year-old Johnson County man could be charged with murder and aggravated assault in the shooting of Tiller, who had been shot before by an anti-abortion foe.
The crime has drawn condemnation and outrage from the president and stirred strong emotions across the nation.
Tiller, 67, was shot once just after 10 a.m. Sunday as he stood in the lobby of Reformation Lutheran Church, 7601 E. 13th St., where he was serving as an usher. The gunman threatened to shoot two men who tried to apprehend him.

According to The New York Times,

moments after services had begun at Reformation Lutheran Church, Dr. Tiller, who was acting as an usher, was shot once with a handgun, the authorities said. The gunman pointed the weapon at two people who tried to stop him, the police said, then drove off in a powder-blue Taurus. Dr. Tiller’s wife, Jeanne, a member of the church choir, was inside the sanctuary at the time of the shooting.
The police in Wichita described the man who was detained as a 51-year-old from Merriam, a Kansas City suburb, but declined to give his name until he was charged. The Associated Press reported that a sheriff’s official from Johnson County, Kan., where the man was taken into custody, identified him as Scott Roeder.