What horror film, typically involving a violent psychopath stalking and murdering several people, was Caitlin Gerard in? 
Smiley
Slasher film
Slasher films are a subgenre of horror films, typically involving a violent psychopath stalking and murdering several people, usually with bladed tools.
 Although the term "slasher" is sometimes used informally as a generic term for any horror movie involving murder, analysts of the genre cite an established set of characteristics which set these films apart from other horror subgenres, such as splatter films and psychological horror films.
Smiley (2012 film)
Smiley is a 2012 American psychological slasher horror film directed by Michael Gallagher and made by Level 10 Films.
 The film stars were Caitlin Gerard, Melanie Papalia, Keith David, Shane Dawson, Andrew James Allen, Toby Turner, and Liza Weil.
 The film was released on October 12, 2012.
David Carpenter
David Joseph Carpenter (born May 6, 1930), a.k.a. the Trailside Killer, is an American serial killer known for stalking and murdering his victims in State Parks in California.
 Carpenter killed several people on hiking trails near San Francisco, California.
 Carpenter killed at least 10 people, with one attempted victim, Steven Haertle, surviving.
 Carpenter used a .38 caliber handgun in all but one of the killings, with a .44 caliber handgun being used in the killing of Edna Kane on Mount Tamalpais. Panic 5 Bravo
Panic 5 Bravo is an action-thriller film directed by Kuno Becker about American paramedics that become trapped on the Mexican side of the border and terrorized by a violent psychopath.
 It was released in the U.S. by Pantelion Films. Polypill
A polypill is a medication that is a drug product in pill form (i.e., tablet or capsule) that "combines" multiple active pharmaceutical ingredients.
 The prefix "poly" means "multiple", referring to the multiplicity of distinct drugs in a given "pill".
 An occasional synonym is "combopill".
 It is commonly manufactured as a fixed-dose combination (FDC) drug product targeting treatment or prevention of chronic disease.
 Polypills may be aimed to be consumed by healthy people as a means of preventive medicine, and/or treating actual pathophysiological condition(s), the former typically involving lower dosages than the latter.
 Polypills can reduce the number of tablets or capsules (generally orally administered) that need to be taken, which in turn may facilitate handling and administration of pharmaceuticals as well as alleviate patient pill-burden.
 Sometimes the multiple drugs in a given polypill might all be aimed at a single underlying condition (or, group of related conditions), partly because this expands the pool of potential patients for whom a given combination of drugs/dosages might be appropriate (particularly in the case of mass-produced polypills, i.e. FDCs).
 The term polypill was first coined in the context of cardiovascular disease prevention, but has since gained broader acceptance, including now for combinatorial drug products that existed before the term was actually coined (as the bare term without any modifiers is now quite generic). Behavioral Analysis Unit
The Behavioral Analysis Unit (BAU) is a department of the United States Federal Bureau of Investigation's National Center for the Analysis of Violent Crime (NCAVC) that uses behavioral sciences to assist in criminal investigations.
 The mission of the NCAVC and the BAUs is to provide behavioral based investigative and/or operational support by applying case experience, research, and training to complex and time-sensitive crimes, typically involving acts or threats of violence. The Assignment (2016 film)
The Assignment (also known as Tomboy, and formerly known as (Re) Assignment and Tomboy: A Revenger's Tale) is an American crime thriller film directed by Walter Hill and co-written by Hill and Denis Hamill.
 The film stars Michelle Rodriguez, Tony Shalhoub, Anthony LaPaglia, Caitlin Gerard and Sigourney Weaver. Holiday horror
Holiday-themed horror films, holiday horror or christmas horror, are a horror subgenre of slasher films and typically involve a psychopathic killer stalking a sequence of victims in a violent manner during Christmas.
 The murders often are conducted with a bladed tool such as a knife, machete, or axe by someone dressed as Santa Claus, a snowman, an elf, or another Christmas character. Mikey (film)
Mikey is a 1992 horror-thriller film directed by Dennis Dimster and starring Brian Bonsall.
 The film centers on the character of Mikey, a young boy who is adopted by a family after his previous adoptive family dies.
 Rather than the darling child they expected, however, Mikey turns out to be a violent psychopath and a budding serial killer. Pocket Listing (film)
Pocket Listing is a 2016 American neo-noir black comedy film directed by Conor Allyn, written by James Jurdi, and starring Jurdi, Logan Fahey, Caitlin Gerard, Christos Vasilopolous, Jessica Clark, Rob Lowe and Burt Reynolds.
 The film was acquired by Metro-Goldwyn-Mayer and Orion Pictures for limited theatrical and video on demand release on December 2, 2016.