Victims of the Tulsa medical center mass shooting include 2 doctors, a receptionist, and a patient

• A gunman killed four people at a Tulsa medical center in a mass shooting on Wednesday.
• Police on Thursday identified the victims, which include two doctors, a receptionist, and a patient.

Authorities on Thursday identified the four victims who were killed by a gunman in a mass shooting at a Tulsa medical center this week.

A 45-year-old man opened fire inside the Natalie Medical Building at the St. Francis Hospital in Tulsa, Oklahoma, on Wednesday evening, armed with a handgun and a rifle, which police said he bought just hours before the attack.

The gunman, who officials said was targeting a doctor he blamed for back pain after a recent surgery, killed four people in the medical center before he died from a self-inflicted gunshot wound.

Tulsa Police Chief Wendell Franklin said at a Thursday press conference that authorities found a letter at the scene in which the gunman said he planned to kill his surgeon and was prepared to shoot "anyone who got in his way."

Here's what we know of the victims so far, according to accounts from authorities and victims' families.

Dr. Preston Phillips

Dr. Preston Phillips was remembered by his friend, Sandy Thompson, as a "wonderful, gentle, kind person with an infectious smile and kind word for everyone."

"He made the world a better place and Preston's presence will be deeply missed," Thompson told CNN.

Phillips was the orthopedic surgeon who performed the gunman's back surgery last month. Police say the shooter called the medical center several times in the aftermath of his surgery complaining of ongoing pain and asking for additional assistance. The shooter saw Phillips again on Tuesday and called once more on Wednesday before the attack.

According to a profile on the clinic's website, Phillips had an interest in spinal surgery and joint reconstruction. He had also previously served as the head doctor for the WNBA Tulsa Shock before the franchise departed the state, The Tulsa World previously reported.

A surgical technician at St. Francis Hospital told CNN that Phillips traveled regularly with a nonprofit organization focused on providing surgical services to underserved areas in the US and Africa. The technician said she and Phillips went on several medical mission trips to Africa, where he impacted numerous people's lives.

Phillips was scheduled to travel to Togo for such a mission in mid-June, the outlet reported.

Dr. Cliff Robertson, president and CEO of Saint Francis Health System, said Phillips was "a man that we should all strive to emulate."

Dr. Stephanie Husen

Dr. Stephanie Husen, a doctor of osteopathic medicine at St. Francis, was remembered by Robertson as "an incredible person."

Her ex-husband John Reckenbeil told The Washington Post on Thursday that Husen was "completely genuine" and "the smartest person in the room."

Reckenbeil said he met Husen, a former physical therapist, in 1999 after she had suffered a serious car crash. Her rehabilitation journey ultimately helped her realize that she wanted to be a doctor, he told the outlet.

Amanda Glenn

Amanda Glenn was a receptionist at the Warren clinic in Phillips' office, according to authorities.

She is survived by her husband, Beau Glenn, and two young sons, Gabe Glenn and Ian Glenn. Gabe graduated high school just last month, according to The Tulsa World.

The Sandite High School Baseball team remembered Amanda Glenn as a "devoted wife, mother and friend," in a Facebook post shared Thursday.

"She was on our Booster Club Board and served the baseball boys and coaches selflessly," the post said. "She was the biggest cheerleader for both of her sons and all of our boys!"

Robertson, the St. Francis president and CEO, choked up while speaking about the staff members who were killed.

"The three best people in the entire world, who are the most committed to doing what they do every day, didn't deserve to die this way," he said.

William Love

William Love was the lone patient at the Warren clinic to be killed in Wednesday's attack. Authorities said they received reports that Love held a door shut in an attempt to protect others amid the shooting.

Love's daughter Cheryl Lowry said her father went to the hospital with his wife, Deborah, who was being treated by Phillips. Lowry said both her parents were in the exam room when the gunman entered the hallway.

According to Lowry, Love held the door closed in an effort to protect his wife, prompting the gunman to fire through the door and hit Love.

Lowry told the outlet that her mother put pressure on Love's chest wound until police came to help. He later died at the hospital.

Love was a Vietnam veteran who spent nearly thirty years in the military, Lowry said.

"He was a really good dad and loved his grandkids. He lived for them," she told The Post.