BUFFALO, Minn. (NewsNation Now) —  Three victims of Tuesday’s attack at a Minnesota health clinic remain hospitalized; one in critical condition and two others in fair condition, a hospital spokesperson told NewsNation Wednesday.

Gregory Paul Ulrich, 67, opened fire at the Allina clinic in Buffalo, a community roughly 40 miles northwest of Minneapolis, killing one staff member and wounding four others. He was arrested at the scene. North Memorial Health spokeswoman Abigail Greenheck said one of the five victims were discharged from the hospital Tuesday.

Ulrich was well-known to authorities before the attack and had been unhappy with the care he had received following a back surgery two years ago, Buffalo Police Chief Pat Budke said.

According to a police report, Ulrich threatened to carry out a mass shooting at the clinic in October 2018, with a doctor telling investigators that Ulrich had talked about “shooting, blowing things up, and practicing different scenarios of how to get revenge.” He said Ulrich told him he dreamed about exacting revenge on the people who “tortured” him, referring to issues he had with back surgeries and the medication he was prescribed for them.

Ulrich told police he had just been telling the doctor about his dreams and that he wouldn’t act on them. Police took him for a mental health evaluation at a facility in Monticello, the report says.

The clinic staff believed Ulrich would act on those threats so they filed paperwork barring him from the company’s property, which police delivered to his home the next month.

A criminal charge of violating a harassment restraining order was filed a couple of weeks later. The nature of that violation isn’t clear in court papers, but orders filed in that case in 2018 and 2019 prohibited Ulrich from having contact with a man whose name matches that of the doctor named in the police report. It wasn’t known Wednesday if the doctor was among the victims of Tuesday’s attack, and a call to his home number rang unanswered.

The charge of violating the restraining order was dismissed last April when the prosecutor said Ulrich was found “mentally incompetent to proceed.”

During a search of the clinic, investigators found a 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. 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.

“We have had several calls for service dating to 2003,” Deringer said.

Court records for Ulrich list a handful of arrests and convictions for DWIs and possession of small amounts of marijuana from 2004 through 2015, mostly in Wright County.

A court services agent who conducted a pre-sentence investigation wrote in a June 2019 filing that he had just learned that Ulrich had applied to police for a “permit to purchase” — apparently meaning a permit to buy a gun — but had not yet been approved. The agent said he “highly recommended” that Ulrich “not be allowed to have use of or possession of any dangerous weapons or firearms as a condition of his probation.”

Ulrich also had raised concerns at a local church. According to an August 2019 update on the Zion Lutheran Church’s website, the church said it had obtained a no-trespassing order for Ulrich after the pastor received a disturbing letter. Church staff were given a picture of Ulrich and told to call 911 if he appeared on any of the church’s properties.

As of Wednesday, Ulrich remains jailed in Wright County and is expected to appear in court Thursday.

The Associated Press contributed to this report.