Pathologists perform autopsies to determine cause of death and contributing factors. In the June 12, 2016 mass murder in Orlando, the immediate cause of death of 49 people plus the shooter was gunshot wounds. The most important contributing factor was bigotry. A second was easy access to guns, particularly an assault rifle. Let's examine these in more detail
First, bigotry. Webster defines bigotry as "1. Stubborn and complete intolerance of any creed, belief or opinion that differs from one's own. 2. Actions, beliefs, prejudices, etc of a bigot." Thus one who is completely intolerant of Christians or Muslims, or Jews, or gays, or people of Mexican heritage could be considered a bigot. Racism should be considered a subset of bigotry. Webster defines racism as "1. A belief that human races have distinctive characteristics that determine their respective cultures, usually involving the idea that one's own race is superior and has the right to rule others." When Muhammad Ali (then Cassius Clay) returned from the Rome Olympics in 1960 as light heavyweight gold medalist, he entered a restaurant in Louisville, Kentucky, his home town. He was turned away by the owner who said, "We don't serve niggers." That is racism. A slightly more subtle example of racism is the assertion that President Obama was born in Kenya, a black outsider. It would be unseemly to refer to the President with the N word.
Racism is a term that is increasingly misused. Mexicans or Jews or Indians are not a race; nor are Africans. In fact, there is more genetic diversity among all the Africans than there is between Africans of one tribe and any specific group of European whites. Genetic analysis has shown that humans are 99.9% the same worldwide. Analysis of the genetic composition of people on all the different continents shows gradual variation of many traits. In America, race is usually defined by skin color, a single criterion that would make both geneticists and anthropologists cringe. Race is more of a social construct than genetic. Paul Ryan, Speaker of the House, called Donald Trump's remarks about a federal judge of Mexican heritage, "racist." He is wrong. Donald Trump's characterization of the judge was bigoted, not racist.
The killer in Orlando had previously expressed hatred for blacks, gays, and women. He would therefore qualify as a bigot and a racist (as we in the USA misuse the term.) The nightclub he shot up was a gay club that was having a Latino night. We do not know if Donald Trump's recent denigration of people of Mexican descent, whether itinerant farm workers or federal judges, was a contributing factor in the killer's decision to shoot up the night club on that particular night, but it might have been.
The killer also claimed that he was inspired by ISIS and pledged allegiance to them. ISIS is a radical Islamic organization that intends to establish a world-wide Caliphate. They are Sunni Muslims, intolerant of other Islamic sects, as well as Christians and Jews, and murderous in the pursuit of their goals, thus qualifying as bigots. Ironically, Islam does not assert that any race is superior to any other. The Islamic definition of a superior person is one who is most in tune with and submissive to Allah. Thus the Orlando killer, who identified as a Muslim, could be criticized as being a bad Muslim for his racial bigotry. Islam does hold homosexual acts to be sins and punishable crimes, so the Orlando killer's bigotry in this case could have been derived from his religion. However, there is a lot of anti gay bigotry among many different civilizations and religions, including Christianity and Judaism, right here in America. Gays have been the victims of many murderous attacks perpetrated by non Muslims.
An additional possibility has arisen to partially explain the shooter's anti gay attitude. He had frequented the Pulse nightclub on several occasions and was recognized on gay dating websites. This suggests that he was a self-loathing gay man. His religious beliefs may have made him murderously enraged by who he really was. If true, that is a disastrous conflict between religious belief and reality and, it is not confined to Islam.
Many sects of Islam, such as the Wahabi sect in Saudi Arabia, treat women as second class citizens. This is well-known. Other Islamic sects are more liberal. Christianity and Judaism are not immune to this, either. One only need be reminded that women did not get the right to vote in federal elections in the USA until the Nineteenth Amendment was ratified in 1920. Black men gained the right to vote when the Fifteenth Amendment was ratified in 1870. For fifty years, all women were subordinated to black men with regard to the right to vote. And, the right to vote for blacks, supposedly guaranteed by the Fifteenth Amendment, was frustrated in the South by Jim Crow laws until 1964 and 1965 when the civil rights bills were passed. Southern states, after voting rights legislation was passed, continued to resist allowing blacks to vote by various legal maneuvers, including obvious voter suppression laws, even now being enacted by Republican-controlled legislatures. Bigotry based on African ancestry and skin color is, unfortunately, alive and well in America today.
Thus the bigotry of the Orlando killer had roots both in his religion and possibly in the fact that he lived in Florida, a southern state with Republican-controlled legislative and executive branches of government.
Easy access to guns: the Second Amendment to the constitution reads, "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed." In 2010 in McDonald v City of Chicago, the Supreme Court ruled (5-4) that this guarantees all individuals the right to own a gun. Previously the courts had held that the Second Amendment was about the rights of the various states to have militias. The National Guard of each state would be an example.
The United States is saturated with guns, an estimated 300 million, or 88 for every 100 individuals in the society. For this "freedom" we pay about 33,000 lives per year in gun deaths. States such as Florida even have "stand your ground" laws which entitle their citizens to shoot other citizens if they feel threatened. George Zimmerman was acquitted of the murder of Trayvon Martin because of the provisions of this law.
Throughout the USA, there is a system of background checks that are supposed to be conducted before anyone purchases a firearm from a store. Private sales and sales at gun shows are exempted These checks are designed to reveal previous criminal records or histories of mental illness. There are many, many examples of failures in the system so that crazy people can easily get guns. The assault rifle the Orlando killer used was purchased legally. He had been investigated twice by the FBI for possible terrorist sympathies but they concluded nothing. The National Rifle Association and conservative members of Congress have resisted almost all efforts to have tighter background checks, require safety courses, require licensure, require liability insurance, prevent gun purchases by people on terror watch lists, or basically anything that would restrict the right of anyone to obtain firearms. Indeed, after the Sandy Hook shooting in 2012, in which a disturbed young man, using his mother's assault rifle, shot 20 elementary school kids aged 6 and 7, Congress did nothing at all. That's not quite right, they observed a moment of silence. They also stood for a moment of silence after the Orlando massacre. Then Speaker Ryan ruled out of order an attempt by Democrats to open a discussion on gun control.
In a comment on the Orlando killings, one Imam was quoted as saying that such a tragedy was unpredictable. This is clearly wrong. Mass shootings are part of American life and can be expected to continue as long as enough members of Congress and State Legislatures are in the pocket of the NRA.