Question: How many horses died in the deadliest mass murder to take place at a school in United States history?

Context articles: Pleasure riding
Bath School disaster
Equine drug testing
Omar Mateen
Westroads Mall shooting
List of attacks related to primary schools
Andrew Kehoe
Oikos University shooting
2016 Orlando nightclub shooting
Wah Mee massacre

Pleasure riding is a form of equestrianism that encompasses many forms of recreational riding for personal enjoyment, absent elements of competition.
 Pleasure riding is called "hacking" in British English, and in parts of the eastern United States and Canada.
 In the United States, particularly the American west, the term trail riding is used to describe pleasure riding, particularly on public lands.
 Many horses are suitable for pleasure riding, including grade horses and other animals of ordinary quality and good disposition.
 Such horses are sometimes called "hacks," particularly in areas where pleasure riding is known as hacking.
The Bath School disaster, sometimes known as the Bath School massacre, was a series of violent attacks perpetrated by Andrew Kehoe on May 18, 1927 in Bath Township, Michigan, which killed 38 elementary schoolchildren and 6 adults and injured at least 58 other people.
 Kehoe killed his wife and firebombed his farm, then detonated an explosion in the Bath Consolidated School before committing suicide by detonating a final device in his truck.
 It is the deadliest mass murder to take place at a school in United States history.
Equine drug testing is a form of drug testing applied to performance horses in regulated competition.
 Most common in racehorses, drug tests are also performed on horses in endurance riding and in international competition such as the Olympics and FEI-sanctioned competition.
 Many horses in competition sanctioned by various national organizations, such as the United States Equestrian Federation in the USA are also tested for improper drug use.
Omar Mir Seddique (November 16, 1986 - June 12, 2016), also known as Omar Mateen, was an American mass murderer who killed 49 people and wounded 58 others in a mass shooting at the Pulse gay nightclub in Orlando, Florida, on June 12, 2016, before he was killed in a shootout with the local police.
 It was both the deadliest shooting by a single shooter and the deadliest act of violence targeting LGBT people in United States history.
The Westroads Mall shooting was a mass shooting that occurred on December 5, 2007, at a Von Maur department store in Westroads Mall in Omaha, Nebraska.
 The gunman, nineteen-year-old Robert A. Hawkins, killed eight people and wounded four, two of them critically, before committing suicide.
 It was the deadliest mass murder in Nebraska since the rampage of Charles Starkweather in 1958.
This is a list of attacks related to primary schools.
 These are attacks that have occurred on school property or related primarily to school issues or events.
 A narrow definition of "attack" is used for this list to exclude attacks during warfare, robberies, gang violence, political or police attacks (as related to protests),accidents, single suicides, and murder-suicides by rejected spouses or suitors, as they are not the type of mass murder event that is the focus of concern.
 Incidents that involved only staff who work at the school have been classified as belonging at List of workplace killings.
 It also excludes events where no injuries take place, if an attack is foiled.
 Accounts without reliable sources have been deleted.
Andrew Philip Kehoe (February 1, 1872 – May 18, 1927) was an American farmer and treasurer of his township school board, notable as a mass murderer for killing his wife and 43 other people (including 38 children), and injuring 58 people by setting off bombs in the Bath School disaster on May 18, 1927.
 He committed suicide near the school by detonating dynamite in his truck, causing an explosion which killed several other people and wounded more.
 He had earlier set off incendiary devices in his house and farm, destroying all the buildings, as well as killing two horses and other animals.
The Oikos University shooting occurred on April 2, 2012, when a gunman shot at people inside Oikos University, a Korean Christian college in Oakland, California, United States.
 Within a few hours, the number of reported fatalities reached seven.
 43-year-old One L. Goh, a former student at the school, was taken into custody and identified as the suspect in the shootings.
 Along with the California State University, Fullerton massacre, this was the fourth-deadliest university shooting in United States history, after the Virginia Tech massacre, the University of Texas Clock Tower shooting, and the Umpqua Community College shooting, and the eighth-deadliest U.S. school massacre overall.
 It is also considered the deadliest mass killing in the city's history.
On June 12 , 2016, Omar Mateen, a 29-year-old security guard, killed 49 people and wounded 58 others in a terrorist attack/hate crime inside Pulse, a gay nightclub in Orlando, Florida, United States.
 He was shot and killed by Orlando Police Department (OPD) officers after a three-hour standoff.
 Pulse was hosting a "Latin Night" and thus most of the victims were Latinos.
 It was both the deadliest mass shooting by a single shooter and the deadliest incident of violence against LGBT people in United States history.
 It was also the deadliest terrorist attack in the United States since the September 11 attacks in 2001.
The Wah Mee massacre () was a multiple homicide that occurred on February 18, 1983, in which Kwan Fai "Willie" Mak, Wai-Chiu "Tony" Ng, and Benjamin Ng gunned down fourteen people in the Wah Mee gambling club at the Louisa Hotel in Chinatown-International District, Seattle.
 Thirteen of their victims lost their lives, but one survived to testify against the three in the high-profile trial.
 It is the deadliest mass murder in Washington state history.