A bomb threat at a home in Oklahoma has been linked to the deadly shooting at a hospital, where four civilians were killed.
Tulsa Police Department confirmed earlier on Wednesday (local time) that five people had been killed at St Francis hospital campus, including the gunman.
It was already confirmed the gunman, who has not been identified, entered the hospital with a rifle and a shotgun, however, Muskogee Police Department has now confirmed a bomb threat was also called in.
Tulsa Police Department tipped off officers from Muskogee, who believed the gunman may have left a bomb at the home, 2News Oklahoma reported.
The distance between the hospital and the home where police believe the bomb may have been is roughly 75km and residents in the area were told to stay inside their homes.
Local news station KTUL reported people were also asked to avoid the Country Club area.
There were no explosives found at the home.
Police have not released the name of the shooter, describing him only as a man aged between 35 and 40 years old.
It is believed the man died from a self-inflicted gunshot wound.
Tulsa Police Captain Richard Meulenberg told CNN the investigation is ongoing.
“So we're still working with other agencies and other jurisdictions as this is related to a much bigger issue with this shooter,” he said.
He also said police do not believe anyone else is in danger. The gunman targeted the second floor of the hospital which houses an outpatient surgery centre, a breast health centre and an orthopaedic clinic.
Capt Meulenberg said the shooter went in "with purpose".
Capt Meulenberg, from the Tulsa Police Department, said as many as 10 people could have been injured in the mass shooting.
Police first received the report of shots being fired at the hospital at 4.52pm (local time) and by 5.01pm, officers had made contact with the shooter.
“It appears both weapons at one point or another were fired on the scene,” Tulsa Police Department Deputy Chief Eric Dalgleish said according to the Associated Press.
“The officers who arrived were hearing shots in the building, and that’s what led them to the second floor.”
There have been 233 mass shootings in the US so far this year, according to the Gun Violence Archive.
Last week 19 children and two teachers were killed by a gunman at Robb Elementary School in Uvalde, Texas. Earlier in May, 10 people were shot dead in a supermarket in the state of New York.
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