BUFFALO, N.Y.. — "I was walking up from the students parking lot, and then all of a sudden saw a bunch of police officers coming together and thought - that's a little unusual," said medical student Joshua Balderman.

Medical students, hospital staff and patients were stranded outside or inside of ECMC Wednesday morning, as police searched for the shooter.

"A few of my friends have texted me and they're stuck inside, so they're just wondering where I was, want to make sure I was safe," said medical student Nikita Patel.

The hospital was locked down for about four hours during the search. Juan Rivera's daughter was inside the hospital's G.I. unit when the shooting took place in an adjacent building.

"The nursing staff were calling from floor to floor, and talking to each other, and they would inform her, because she was pretty well distraught," said Rivera.

Eventually, the lock down was lifted, and people were permitted to go back inside the building, but Rivera said the incident is exactly the type of thing you worry about as a parent.

"You know, when your child is distraught and in need and they're calling out for you, and you know you can't do anything because your hands are tied," he said.

At the time of the shooting, hospital officials say there were about 400 patients at ECMC, and about 1,000 other employees. They say, their immediate goal was to make sure everyone was kept safe.