(CNN) In the past three months, investigators have conducted dozens of interviews and reviewed journals, records and electronic files of a gunman who killed two and injured four others at a Florida hot yoga studio.

What they found was months of planning and a history of hatred toward women, Tallahassee Police Chief Michael DeLeo said in a Tuesday afternoon news conference.

Maura Binkley, 21, and Nancy Van Vessem, 61, were fatally shot when a gunman opened fire on their class at Hot Yoga Tallahassee on November 2. Four others were shot and one pistol-whipped before the gunman fatally shot himself, police said.

DeLeo said there is substantial evidence that the gunman, 40-year-old Scott Beierle, "pre-planned this attack" after demonstrating a "lifetime of misogynistic attitudes."

The gunman purchased the handgun used in the shooting in July 2018 and the following month called the yoga studio and conducted a search for a map of its building, DeLeo said.

Read More