Author John Cook discusses of a new report that says the vast majority of studies say humans play a role.
A Colorado man who had just been released from jail on domestic violence charges shot and killed three people Tuesday, including his ex-girlfriend, who was on the phone with a 911 dispatcher when she was killed, authorities said.
The gunman then shot and killed himself, Weld County Sheriff John Cook said.
The victims included the ex-girlfriend's sister and the sister's husband. All were found dead in a home in unincorporated Weld County outside Longmont, about 35 miles north of Denver.
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