LEBANON, N.H. -- A patient was shot to death inside an intensive care unit Tuesday by her son, leading to a lockdown at New Hampshire's largest hospital, authorities said. No one else was injured.

Authorities said Travis Frank, 49, of Warwick, Rhode Island, was arrested and will be arraigned Wednesday on first-degree murder charges for the shooting shortly before 3 p.m. at Dartmouth-Hitchcock Medical Center in Lebanon.

Attorney General Gordon MacDonald identified the victim as Frank's 70-year-old mother, Pamela Ferriere, of Groton, New Hampshire.

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No possible motive for the shooting was released.

Earlier, Authorities said a person was taken into custody shortly before 3 p.m. while trying to leave the grounds of Dartmouth-Hitchcock Medical Center in Lebanon.

An active shooter alert was issued after police received a report of a shooting inside an ICU on the fourth floor of one of the buildings.

Rhode Island State Police said the suspect's car had Rhode Island plates so police in New Hampshire reached out to the state's Fusion Center, an information center under the command of the state police that also involves representatives from local, state and federal agencies.

The center helped identify the suspect as a Rhode Island resident, said Laura Meade Kirk, a state police spokeswoman.

John Kacavas, the medical center's chief legal officer, thanked police and the attorney general's office for their response to a "tragic situation."

People were told to avoid the area around the hospital, and traffic was stopped on a route leading to the medical center.

The Bureau of Alcohol, Tobacco, Firearms and Explosives and Vermont State Police assisted New Hampshire and local police.

CBS affiliate WCAX-TV reports that an employee said all workers received an email from the hospital about a "code silver," telling them to get out if possible and otherwise to shelter in place. "Code silver" indicates that a violent situation is unfolding.

The incident started at about 1:30 p.m., when police received a report of an active shooter, WCAX reported. SWAT teams as well as officers responded.

The state attorney general's office is investigating.