Word spread through an Oregon hospital last month that a visitor was causing trouble in the maternity ward, and nurses were warned the man might try to abduct his partner’s newborn.

Hours later, the visitor opened fire, killing a security guard and sending patients, nurses and doctors scrambling for cover.

The shooting at Legacy Good Samaritan Medical Center in Portland was part of a wave of gun violence sweeping through U.S. hospitals and medical centers, which have struggled to adapt to the growing threats.