So you're sure he was a Christian? I really don't know.
According to an old Time Magazine article posted at
http://www.cnn.com/ALLPOLITICS/1996/analysis/back.time/9606/10/index.shtml (I know, I know...Time and CNN...but still), Sirhan came from a Greek Orthodox background and attended Evangelical Lutheran schools. The Sirhan family came to the US in 1957, sponsored jointly by UNRWA and the World Council of Churches. Sirhan was a resident alien of the US and a citizen of Jordan.