The family of the U.S. ambassador to Libya killed there Tuesday during a protest over a film that ridiculed Islam's Prophet Muhammad, said Wednesday that he was a passionate believer in Libyan culture and would not want his death to sour the outlook for its potential.

Ambassador J. Christopher Stevens, 52, was killed Tuesday night when he and a group of embassy employees went to the consulate to try to evacuate staff as the building came under attack by a mob with guns and rocket propelled grenades, according to Libyan officials.

Three members of Stevens' staff were also reportedly killed.

Stevens' stepfather, Oakland resident Robert Commanday, said Wednesday the family is distraught and reeling from the tragedy but that he wanted to share some thoughts about his stepson, "who in 36 years I never saw lose his temper."

"He was calm and cool and happy, and people loved him because he was interested in them," Commanday said.

Stevens had been passionate about languages and exploring the world since he was a young man, launching a career in international work when he taught English to Berbers in Morocco for the Peace Corps, Commanday said.

When Secretary of State Hilary Clinton sent Stevens to Benghazi during the Libyan rebellion, Commanday said, he developed a strong affection for, and belief in, the people who lived there.

"He wouldn't just stay in his office. He'd go out into the street and meet the people, mix it up with them. I know he had a feel for their culture," Commanday said.

That was the irony in Stevens' death, Commanday said: "He was murdered by the people he loved, the people he was trying to help."

Despite the tragedy and the pain of the death, Commanday was quick to add, "I don't think he would want anyone to take it out on the Libyan people. There's a personal reaction, a knee-jerk anger, to see him trying to do so much for them and giving his whole career to them and then they destroy him.

"But he would want people to believe in the people he believed in, and that democracy is possible in places like that, and Tunisia and even Syria. He believed in these cultures and their potential and possibilities. He was passionate, and I think he'd want people to remember that."

There will be a Bay Area memorial for Stevens but the details have not been planned yet, Commanday said.

The protest was sparked by outrage over a film ridiculing Muhammad produced by an Israeli filmmaker living in California and promoted by an extreme anti-Muslim Egyptian Christian campaigner in the United States. Excerpts from the film dubbed into Arabic were posted on YouTube.

The Associated Press contributed to this report.