STARKE, Fla. — Nine years after he calmly shot and killed an abortion doctor and his safety escort outside a Pensacola clinic, Paul Jennings Hill died by lethal injection here on Wednesday as his supporters declared him a martyr and warned that they might replicate his action.

Hill, a former Presbyterian minister, is the first killer of an abortion provider to be executed in the United States. He had not tried to prevent his death, which took place at Florida State Prison, just after 6 p.m. as lightning jagged across a nearly black sky. But abortion advocates fear what Hill's followers have hinted for months: that his death will spur a wave of violence against abortion clinics, many of which have operated in relative peace over the past few years.

Addressing reporters in a final interview here on Tuesday, Hill made the same prediction.

"I believe in the short and long term, more and more people will act on the principles for which I stand," he said. Hill also said that while it was not his choice to die, "I'm willing and I feel very honored that they are most likely going to kill me for what I did."

Last month, the state attorney general, Charlie Crist, and two top prison officials received death threats in letters that contained bullets.

As the hour of the execution approached, protesters gathered in a field across from the prison in three areas: one for Hill supporters, one for Hill opponents and the third for those against the death penalty. Most of the roughly 50 supporters of Hill were white men, some kneeling and praying, others singing "How Great Thou Art." Abortion rights advocates said they planned to attend the execution and press their cause, but there was not a single person representing that movement. Three protesters said they were there to condemn Hill's violent act. About 20 others came to oppose the death penalty.

Sterling Ivey, a spokesman for the Florida Department of Corrections, told reporters on Wednesday evening that Hill was pronounced dead at 6:08 before 24 witnesses. Just before receiving his injection, Hill said: "If you believe abortion is an evil force, you should oppose the force and do what you have to, to stop it."

Hill's final statement was preceded by claps of thunder that were audible in the death chamber, Sterling said.

In the field across the highway, some of Hill's supporters knelt and shouted "Speak Your Wrath, Lord!" as inky clouds surrounded the prison and thunder boomed. At 6 o'clock sharp, the group released yellow balloons into the sky and a few men sobbed. The rain started then, and did not let up for hours.