An attorney representing a 25-year-old woman says his client had "no real response whatsoever" when he told her that four people were killed after she crashed her car into an Oklahoma State homecoming parade.

Tony Coleman told NBC's "Today" show Monday that Adacia Chambers was hospitalized two years ago for an unspecified mental illness. He says he believes Chambers wasn't under the influence of alcohol or drugs at the time of Saturday's crash, but that she was mentally ill.

But Stillwater Police Capt. Kyle Gibbs said authorities believe Chambers was under the influence of alcohol or drugs. Gibbs told ABC's "Good Morning America" Monday that authorities haven't seen signs of mental illness in Chambers, though she has made no statements to investigators so far.

Gibbs says 17 people remain hospitalized, including five in critical condition.