Two men were seriously injured near Fort Detrick, an army base in Frederick, Maryland, on Tuesday morning and the person who shot them, a US navy hospital corpsman, is dead, according to the authorities.
In Chicago, seven people were shot and wounded in a burst of gun violence.
The seven were involved in a fight on the sidewalk when shots were fired about 11.10pm (local time) on Monday in the Englewood neighbourhood on Chicago’s South Side, police said. A 39-year-old woman was hospitalised in serious condition after she was shot in the arm and abdomen, police said.
Five men were hospitalised in fair condition, while another person was in good condition after walking into a hospital in the Cook County suburb of Harvey with a gunshot wound to the leg, police said.
No one was in custody on Tuesday morning and detectives were investigating.
The Maryland police responded to reports of gunfire at a business park on Progress Drive at about 8.20am (local time) , Jason Lando, the police chief in Frederick, said at a news conference.
Chief Lando said the gunman shot two men at the Riverside Tech Park. They were flown by helicopter to a shock trauma centre in Baltimore, where they were in critical condition, Chief Lando said.
The US navy confirmed that the shooter was a navy hospital corpsman but did not identify him.
The gunman then drove about 10 minutes to Fort Detrick, which is about 50 miles northwest of Washington and 20 miles south of Camp David.
As the police began rushing to Fort Detrick, they learned that personnel at the base had shot the gunman.
He had breached a gate at the base just off Opossumtown Pike, the Fort Detrick police said.
The Fort Detrick police said that they “neutralised an active shooter situation” and that “medical life-saving procedures were initiated”.
The gunman, who Chief Lando said was 38, was pronounced dead at the scene, according to the Fort Detrick police.
Chief Lando said that the police were still trying to learn about any relationship between the gunman and the victims, why he targeted the business park and where exactly the shootings took place.
He described the Riverside Tech Park as a “row of businesses” where the shooter opened fire.
Michael O’Connor, the mayor of Frederick, said in an interview that there was no reason to believe the shootings were a “random act”.
“What I’ve heard is that it’s likely that the individuals are at least aware of one another,” O’Connor said. “What caused this to turn into an incident like this — it’s difficult because they haven’t been able to talk to the victims yet.”
Chief Lando said that the shooter went into a business in the industrial park and that people fled from the building. He did not identify the business the gunman entered.
The shootings on Tuesday occurred two weeks after a gunman killed 10 people at a grocery store in Boulder, Colorado. The shooting in Colorado came only six days after eight people were killed in shootings at three massage businesses in the Atlanta area.
The shooting in Chicago comes amid recent violence in the city. The day before, on Easter Sunday, separate shootings across Chicago left seven people dead and at least 10 more with gunshot wounds.
Last week, a 13-year-old boy, Adam Toledo, was fatally shot by a Chicago police officer after he ran from officers while carrying a handgun. He died at the scene on March 29 and a gun was recovered.
Mayor Lori Lightfoot said on Monday that she had directed the Chicago Police Department to capture and bring to justice whoever gave the boy the handgun. Last week, the department reported that by March end there were 131 homicides compared with 98 for the same period last year.
New York Times News Service and AP