Washington: Police arrested a gunman suspected of killing three people and wounding two at a suburban Maryland business park before shooting another man in neighbouring Delaware.
"The suspect in this incident has been located and is in police custody," the Wilmington, Delaware police department said of Radee Prince, 37.
Wilmington Police Chief Robert Tracy earlier told reporters that Prince "is a dangerous individual. This person shot six people in one day" in attacks that were not random.
Read: US: 3 killed in shooting at business park in Maryland; hunt on for suspect
Prince had been sought "in connection with both a multiple shooting incident early Thursday morning in Edgewood, Maryland and another shooting incident at mid-morning" in Wilmington, Delaware, a statement from police said.
Harford County Sheriff Jeffrey Gahler said three people died in the first incident at a granite business just before 9:00 am (local time).
He confirmed a handgun was used and two other victims were transported to trauma centres in serious condition.
When the shooter was still at large, several Edgewood- area schools were placed on lockdown, officials said, while the nearby set of popular Netflix show "House of Cards" was also reportedly secured.
Gahler said Prince was associated with the company, Advanced Granite Solutions, where the first shooting occurred, near Baltimore.
"This does appear to be a targeted attack, limited to that business," he said.
Police were investigating Prince's connection with the firm, where all five victims of the first shooting were employed, Gahler said, declining to give further details about them.
He said other people beside the five victims were on the premises when the shooting took place.
Tracy said the victim in the second shooting identified the gunman.
"They're known to each other and they've had some past history," he told a news conference.
The suspect fled the first attack in a car registered in Delaware, Gahler said.
Variety magazine reported that the set of "House of Cards," which is partly filmed in Maryland, was placed on lockdown while police searched for the shooter.
The executive producer of the series, Dana Brunetti, addressed the incident in a Facebook post.
"Shooting near House of Cards set," Brunetti wrote.
Some of the school lockdowns were later lifted, according to Harford County Public Schools.
The incident was the latest mass shooting in a country where such killings have become tragically commonplace.
On October 1, a gunman in a 32nd-floor casino hotel room rained fire down on concert-goers in Las Vegas, killing 58 and wounding more than 500.
It was the deadliest shooting in recent US history.
To date in 2017 there have been 286 mass shootings - nearly one per day - according to the online Gun Violence Archive.
