A gunman opened fire in downtown Minneapolis on Tuesday, spraying rounds toward an emergency room entrance at Hennepin County Medical Center.

The gunfire that erupted after a dispute between two groups of people at the hospital shattered windows and hit an SUV during the middle of the afternoon at the busy downtown intersection. No one was injured.

"It was just 'Boom, boom, boom, boom, boom,' " said Rashad Jackson, a cook's assistant at HCMC. He was at his apartment less than a block away when he heard the gunfire.

HCMC immediately went on lockdown as police quickly descended on the area around 3:15 p.m., roped off the crime scene and began looking for suspects. A pile of 23 shell casings were left scattered on the street near the intersection of Chicago Avenue S. and 8th Street, about 100 feet from the hospital entrance.

"We did lock down the hospital for a short time this afternoon while we assessed the security situation," HCMC spokeswoman Christine Hill said. "Once it was determined that there was no risk to the safety of our patients and staff, we returned to normal operations, with the exception of the closure of our 8th Street entrance during the investigation and the increased presence of security and law enforcement officers."

This is the third gun-related incident near the hospital this year, giving rise to safety concerns at a mammoth medical center that specializes in treating victims of the most serious traumas. It was not clear how many people were in the emergency room at the time of the incident, but the department is the busiest in the state, averaging 250 patients a day.

Lt. Richard Zimmerman said a group of people passing through the hospital entrance got into an argument with another group and somebody started shooting.

A Minneapolis homicide detective at the scene said he believes the intended target was someone passing through the hospital entrance. Investigators were looking at the possibility that the incident was connected to a shooting hours earlier near E. 38th Street and Oakland Avenue S. that left two men wounded.

Minneapolis has experienced a growing number of nonfatal shootings this year, in nearly every corner of the city.

A Star Tribune review of Minneapolis police reports found at least 116 confirmed shooting victims between Jan. 1 and July 20.

Police have arrested 46 people after shootings this year, according to the Star Tribune analysis, with some of the alleged shooters having multiple arrests.

Oftentimes, police do not make arrests after the shootings, but they use the data to pinpoint areas where shootings have intensified in order to beef up enforcement in those neighborhoods.

First Precinct Inspector Medaria Arradondo said patients and the public should feel safe and secure around the medical center. "We're certainly taking precautions with their internal security to make sure that public safety is taken care of here at the hospital," he said.

The area near the medical center has already been a hot spot for violence this year.

A woman was shot in the leg on April 30 as she drove past the hospital with another woman and a toddler in her car. Witnesses said they saw a gunman fire at the passing vehicle, then throw the gun down and run into a nearby store. Police officers arrested him there, and prosecutors later connected the shooting to a gang war that had already seen several shootings.

Just two weeks earlier, HCMC went into another rare lockdown after a report of a person with a gun. Police came to HCMC's Red Building off 8th Street and Park Avenue after two visitors had a dispute, and one claimed to have a gun.

A police spokesman said the suspect had left by the time police arrived and that officers did not find a gun. The hospital reopened a few hours later.

Jackson, the witness to Tuesday's incident, said he did not see who fired the shots.

He stood and watched from across the street with other curious passersby as police officers combed the scene for evidence.

"If he had any aim at all, people would have been dead out here," said Jackson.

Matt McKinney • 612-217-1747