Vanessa Marquez as Nurse Wendy Goldman in an episode of "ER."

"ER" actress Vanessa Marquez was shot and killed by police Thursday after she pulled a BB gun on officers, Lt. Joe Mendoza of the South Pasadena Police Department confirmed to USA Today Friday.

Officers thought the weapon was a semi-automatic handgun.

The incident occurred during a welfare check to the 49-year-old's apartment in South Pasadena, California.

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When officers arrived around noon Thursday, they "noticed the female was having seizures" according to a press release received by USA Today Friday. Paramedics were called to assist.

"While speaking to her, officers became aware she was possibly suffering from mental health issues, became uncooperative, and appeared to be unable to care for herself," the statement continued. "They continued to speak to her for over an hour and a half in an attempt to offer her medical care. She then armed herself with a handgun and pointed it at the officers, at which time an officer-involved shooting occurred."

Marquez was then transported to a hospital where she was pronounced dead.

No officers were injured during the incident.

Marquez played Nurse Wendy Goldman in the first few seasons of the NBC hit medical drama series. She also starred in the 1988 teacher drama "Stand and Deliver."