A day after a street fight and shooting that shattered windows and glass doors at the Hennepin County Medical Center, a hospital official praised staff for not letting the violent attack interrupt the emergency room for long.

“We were back to normal operations in less than half an hour,” said Scott Wordelman, a vice president at the medical center.

The shooting is the latest incident to highlight that gun violence is a growing problem for hospitals in Minnesota and around the country. Just this week, there were hospital shootings in New Jersey and Iowa. FierceHealthcare, a leading news source for the health care industry, tallied 150 hospital shootings from 2000 to 2011, with 30 percent in emergency rooms.

It is still not clear what happened outside HCMC, but a shooter or shooters left 23 shell casings scattered at a busy intersection about 100 feet from the emergency room entrance along E. 8th Street. Bullets slammed into hospital windows, shattered the lower half of the emergency room door and sent panicked staff and patients ducking for cover around 3:15 p.m. Tuesday.

A Minneapolis police spokesman said the case remains under investigation. No one has been arrested.

It is the third gun-related incident this year near the hospital, one of the state’s busiest, with an average of 250 people entering the emergency room each day.

Wordelman said the staff constantly evaluates safety issues at HCMC and makes changes when necessary. The hospital is outfitted with cameras, panic alarms, controlled access to the emergency department and 24-hour security guards armed with Tasers. The hospital plans to launch a systemwide communication tool soon and has invested money in staff training to make sure people have the skills necessary to de-escalate tense situations.

“This is an ongoing part of our work,” Wordelman said.

It is much the same at North Memorial Medical Center in Robbinsdale. The security staff is present every hour of every day, along with a security officer stationed in the emergency department. Video cameras in the hospital and emergency department act as a deterrent. If a situation spirals out of control, hospital staff can lock down the department “within seconds,” hospital spokeswoman Lisa Bader said.

“It’s just a flick of a computer switch,” she said.

North Memorial partners with local law enforcement agencies as well and can make calls to get police officer assistance when necessary.

Though shootings are the extreme, violent acts are far more common in and near emergency rooms than most people realize, said Dr. Leigh Vinocur, an emergency room physician and spokeswoman for the American College of Emergency Physicians.

“It’s definitely gone up in the more than 20 years I’ve been practicing,” Vinocur said. “Certainly inner city ERs are beefing up their security. Some are even having metal detectors and things because it’s a problem. But it makes sense, too: The ERs are a microcosm of society so all of these things boil over into the emergency department.”

The emotional toll of injuries, the possibility that patients are high or drunk and emergency rooms’ acceptance of anyone at all hours make them an atmosphere ripe for physical confrontations, said Deena Brecher, president of the Emergency Nurses Association.

“What people don’t understand is that this happens in emergency rooms every day,” Brecher said.

A study that queried 13,000 nurses found more than half reported verbal or physical abuse in the past seven days at work. It is so common that some people within the emergency department just expect bad things to happen, Brecher said. “It’s a severely underreported issue,” she said.

The challenge for a hospital is to balance the need to quickly evaluate incoming patients against protecting hospital staff from whatever comes in through the emergency room door, Brecher said.

Someone should be near the front door to lay eyes on a patient as quickly as possible, but, she said, “you don’t want to be a sitting duck.”