Police have released body camera footage from the shooting in Vegas.
Kirstie Alley believes she has found a common denominator of mass shooters in the US.
The Scientologist, 66, sent a series of tweets saying she believes psychiatric drugs are linked to most massacres.
Her comments came after Stephen Paddock, 64, shot and killed 59 people during a country music festivalin Las Vegas.
Actress Kirstie Alley is a well-known Scientologist. Photo / Getty Images
"We have to solve the mystery of why there were no 'shooters' or almost 0 before the 1980s. I know one common denominator other than guns," Alley tweeted, suggesting Paddock opened fire due to his use of prescription drugs.
Paddock has been prescribed Valium three months before the shooting.
"One additional common denominator of 'shooters' is USA's mass usage of psychiatric drugs. A % do have side effects of VIOLENCE & SUICIDE," continued the outspoken actress and Scientologist.
Twitter users were furious at her comments on the tragedy. One person tweeted back: "Did you really just say that?"
"Yes I did say it. It happens to be a common denominator in shooters ... one that didn't exist before the 80s ... not my opinion. Statistic based," she wrote. "It's an actual bonified black box warning label on these drugs as possible side effects. VIOLENCE & SUICIDE."
Yes I did say it. It happens to be a common denominator in shooters..one that didn't exist before the 80's.. not my opinion. Statistic based https://t.co/M7zopL4Dwl
It actually isn't a tenant.. it's an actual bonified black box warning label on these drugs as possible side effects. VIOLENCE & SUICIDE https://t.co/xR1t1YJ1WA
Alley is one of several celebrity Scientologists who have spoken out against using psychiatric medications. Tom Cruise famously started a feud with Brooke Shields after he attacked her for her use of medication to treat post-partum depression. They buried the hatchet however and Shields attended the star's 2006 wedding to Katie Holmes.
Cruise also had a heated interview with Matt Lauer on the Today show in the US in 2005 over the use of antidepressants.
