A 19-year-old woman opened fire with a rifle in the middle of the Pennsylvania State University campus today, killing one student and wounding another before she was tackled while trying to reload.

The woman, Jillian Robbins, lives in State College, which surrounds University Park, but is not a student at the university. Acquaintances said Ms. Robbins had a history of mental problems.

No immediate charges were filed against Ms. Robbins. The police said that they knew of no motive for the shooting and that Ms. Robbins did not know her victims.

Officials said she fired at least five shots from her rifle, a Mauser with a telescopic sight, around 9:30 A.M., from in front of the Hetzel Union Building, one of the campus's busiest areas, where she had spread a tarp on the lawn. The shots sent hundreds of students and teachers scattering.