Three young transients accused of robbing and killing two people in Northern California have pleaded not guilty to murder charges.

San Francisco news station KNTV reports (http://bit.ly/1LoCqB0 ) that they entered their pleas Thursday in a Marin County Superior courtroom.

Prosecutors allege that 23-year-old Morrison Haze Lampley shot and killed a 23-year-old Canadian backpacker in San Francisco's Golden Gate Park with a stolen gun. Her body was found Oct. 3.

Lampley also is accused of using the same gun to kill a 67-year-old tantric yoga instructor two days later in Marin County.

Prosecutors have charged 18-year-old Lila Scott Alligood and 24-year-old Sean Michael Angold with murder, accusing them of participating in the robberies and killings.

The three were arrested in Portland, Oregon, with the yoga teacher's car and backpacker's camping gear.

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Information from: KNTV-TV.