In any country, let alone one as patriotic as the US, few actions are as provocative as protesting at a soldier's funeral.
The Phelps family pickets mourners across the country, to mark what it describes as God's revenge on the US for tolerating homosexuality.
Their actions are in the name of the Westboro Baptist Church, which numbers 71 and is headed by "Gramps", preacher Fred Phelps. The church, which is based in Topeka, Kansas, mostly comprises his extended family.
Louis Theroux says the Phelpses are the most extreme people he has ever met, which is saying something, and in this interview at the BBC, he talks about how three weeks with them left him perplexed by their motivation.
The family have been in the news recently after the church was ordered to pay nearly $11 million to the the father of a fallen soldier whose funeral was the subject of one of their protests.
And just to add a final element of weirdness to this whole thing, they have a website too: www.thesignsofthetimes.net
Here's an extract from Louis Theroux's program which was originally aired earlier this year:
