When I first found out that the Branch Davidian cult (gunned down by the US government in Waco, Texas) was a schizm of the Seventh Day Adventists, I was shocked. I knew that the Worldwide Church of God also split off of the same religious sect.
At that time, I had not fully accepted that the Worldwide Church of God was a cult*. I found myself compelled to research the history and beliefs of the Branch Davidian cult, to compare it with 'the church' that I grew up in. First, I'll go over the beliefs both the Branch Davidian cult and the Worldwide Church of God had in common:
- Both believed that Christ would return in the immediate future.
- Both kept the Sabbath on Saturday.
- Both kept dietary laws.
- Both kept all of the Jewish Feasts; including the Feast of Tabernacles, Passover, Pentecost, the Day of Atonement, Feast of Unleavened Bread (etc.)
- Both believed they were 'God's one true church.'
- Both groups believed they were the 'Philadelphia church' mentioned in Revelation 3:7
- Both believed their respective leaders were 'God's end time prophets.'
- Both believed in a 'Place of Safety', where members would be called to during the impending apocalypse.
- The Branch Davidians believed they would have to physically fight off the demons of the apocalypse with weapons.
- Worldwide Church of God members awaited the day when trumpets would call them to their 'Place of Safety' in Petra, Jordan. There, 'the church ' would build a great city, and start a new civilization.
- Many Branch Davidians already lived in their 'Place of Safety' (Waco, TX) and stock-piled gun in anticipation of the apocalypse.
Below is a time line, tracing the Branch Davidian cult and the Worldwide Church of God back to the same parent group; the Seventh Day Adventists.
1863: The Seventh-day Adventist Church becomes an official body. Ellen G. White, who was considered an end time prophet, played a big part founding the church. She taught that, when the apocalypse came, Jesus will gather all those who are worthy and take them to a kingdom in heaven. 
1884: Some Seventh-day Adventist members did not believe a woman (Ellen G. White) could be a prophet. These members broke away and formed the Church of God (7th Day). 
1929-1931: Victor Houteff (a minister of the Seventh-day Adventists) believes he is an end time prophet. He began teaching that God will create a place of safety on earth when Christ returns (ruled by Jesus and the "Antitypical David.") The Seventh-day Adventist Church disfellowshipped him for these teachings. Houteff starts his own church, the Davidian Seventh-day Adventists. 
1938: Minister Herbert W. Armstrong was disfellowshiped by the Church of God (7th Day), for preaching about the Feast of Tabernacles and Anglo/British Israelism**; the belief that Anglo-Saxons are the true descendants of the ancient Israelites. Armstrong formed his own church, called the Radio Church of God (later re-named the Worldwide Church of God.) Armstrong claimed to be God's end time prophet. 
1955: The Davidian Seventh-day Adventists are split when their end time prophet Victor Houteff dies. Houteff's wife is appointed leader, but Minister Benjamin Roden claims to be God's new endtime prophet. Roden forms the Branch Davidians. 
** [It is important to note that Anglo/British Israelism was a belief preached by the Ku Klux Klan. ]