One person is dead and another four have been injured after a 67-year-old man unhappy with the health care he had received opened fire at a medical clinic in the US

Bomb technicians were investigating a suspicious device left at the scene in Buffalo, Minnesota, as well as others at a motel where alleged shooter Gregory Paul Ulrich was staying, authorities said.

All five victims were rushed to the hospital before a hospital spokeswoman confirmed the death later on Tuesday. Three of the victims remained in stable but critical condition and a fourth had been discharged.

The attack happened at a clinic in the community of about 15,000 people roughly 40 miles north-west of Minneapolis. Authorities said Ulrich, of Buffalo, opened fire at the facility and was arrested before noon.

Though police said it was too early to tell if Ulrich had targeted a specific doctor, court records show he at one point had been ordered to have no contact with a man whose name matches that of a doctor at the clinic.

As authorities searched the clinic for more victims, they found the suspicious device and evacuated the building, Wright County Sheriff Sean Deringer said.

It was not immediately clear whether that device exploded, but TV footage showed several shattered plate-glass windows at the clinic. Mr Deringer said suspicious devices were also found at a local Super 8 motel where Ulrich had been staying, and there were at least two shattered windows there as well.

Hennepin County Medical Center spokeswoman Christine Hill said Tuesday night that a person brought to the hospital after being shot at the Buffalo clinic had died.

Police Chief Pat Budke said Ulrich has had a long history of conflict with health care clinics in the area.

“All I can say is, it’s a history that spans several years and there’s certainly a history of him being unhappy with health care … with the health care that he’d received,” Mr Budke said.